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My Plan to Achieve Energy Freedom - The Road to Zero Energy Bills

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Comments

  • Registered Users Posts: 466 ✭✭discostu1


    Octopus energy in the UK do this kind of dynamic pricing I don't see it here any time soon plus CRU are determined to start with a 3 tariff maximum. Ecar owners will be watching the space closely. Politicians should be watching it too ….but from the pov of Pensioners/Low wage earners


  • Registered Users Posts: 265 ✭✭Conor20


    Thanks for all of your replies. Apologies for the delay in getting back to reply.
    Alkers wrote: »
    As above, re: financial payback of batteries, divide the cost of the battery by the saving per kWh of electricity to get the number of cycles before the battery will pay for itself. You'll nearly always get a very long period.

    E.g. 13.8 kWh powerwall costs €7,400 (is this excluding installation?). Divided by your (best case) saving of 17c = 43,500 units. Tesla claim 100% depth of discharge so you would need to fully cycle the battery 3,152 times for it to break even.
    Would you cycle a battery that size once a day - I wouldn't think so and even if you did it would take 8.5 years to reach break even point, by when your battery is probably knackered in any case. As I said before, If you don't fully cycle the battery every day, it takes longer. If the usable capacity of the battery is smaller, it takes longer. If the battery degrades, it takes longer. If you have to top-up the battery using night-rate or daytime electricity, it takes longer. If FIT is introduced, it takes way longer.

    Great reply, thanks. It's always useful to work the upper and lower bounds. I'd see an 8.5 year payback best case scenario as not unreasonble for a technology still on the exponential-cost-reducing-curve. That means 4.25 years payback in 18-24 months at the current pace of cost reductions, at least on a product perspective. As you say, installation also costs money and the cost of that is not falling anywhere near as fast, if at all so that will have an impact. It simply comes down to incentives - if batteries give Irish people the ability to reduce their costs, their environmental impact and their contribution to a stable electicity grid, then they should be incentivised to the point that they make pure financial sense to everyone. In terms of working out the payback time, I know that most people use this as their main metric for investment, though I prefer normalizing it to a yearly ROI based on it's warrenty period, and then just invest in the thing that has the highest ROI % per year. That way you can compare it to your mortgage and other alternative investments. The return of €7,400 you estimate over 8.5 years would give an ROI of €7,400 / 8.5 = €870.58 per year, and so €1,305.88 of "profit" over the remaining 1.5 year warrenty period (Powerwalls look to have a 10 year warrenty period (https://www.tesla.com/sites/default/files/pdfs/powerwall/Powerwall_Warranty_USA_2-0.pdf). €1305.88 / 10 = €130.588 per year on a €7,400 investment is a 1.74% yearly ROI best case. Not good enough to justify when you're paying 3.5% on your mortgage, but it's a good baseline to have as prices fall.
    KCross wrote: »
    I'd wonder about that too. Environmentally its surely better to give it to the grid rather than a battery which has had all the associated mining, transport and the need to recycle at the end of its life?

    The environmental (e.g. Carbon reduction) benefit of SolarPV is that it reduces the need for fuel in some power plant when the solar is generating and hence lowering demand. Because the power plants powering the grid change all the time (in Ireland, mostly as a function of how much wind is generating), so too does the CO2 reduction. This is encapsulated in the real-time marginal CO2 intensity figure for the grid at any time. You can see this for Ireland in real-time on the Eirgrid Dashboard (http://smartgriddashboard.eirgrid.com/).

    CO2EmissionsOverTime.png

    It ranges from 500 gCO2 emitted per kWh down to around 150 gCO2 / kWh over this monthly period. This was quite a clean time on the Irish grid - you can see the electricity sources for the last 30 days, and wind powered 53.1% of all electricity consumed in Ireland for the past 30 days:

    PowerGridMakeup_March2020.png

    So this is all just to say that it *when* you feed your power into the grid matters. If your solar generation coincides with the highest marginal CO2 intensity, then feeding it straight into the grid is better (from a CO2 perspective). However, if it doesn't, then it may prevent more CO2 emissions stored in a battery until a grid demand peak coindices with low wind and solar. If you only care about CO2 reduction, then it may also make sense to charge the battery at times of low emissions (usually times of high wind) and feed it back into the grid at times of low wind (and high emissions). Looking at the chart above, if you charged the 13kWh Tesla Powerwall at 150gCO2 / kWh (emitting 13 kWh * 150 gCO2 / kWh = 1.950 kg CO2 ) and then discharged it when the grid was emitting 500 gCO2 / kWh (preventing the release of 13 kWh * 500 = 6.5kg CO2), you would have a net negitive emissions impact of 6.5kg - 1.95kg = 4.55kg CO2. The average Irish person emits about 13,000kg CO2 per year for perspective. So if you managed to do this every day, you'd reduce your net impact by 4.55kg * 365 = 1,660kg CO2 a year. Lots of simplifications here, but just to give an idea of how time of use really matters with energy consumption and storage to optimize your emissions.
    unkel wrote: »
    My battery was end of commercial life (multinational data centre UPS), I got it for free. Methinks it's more environmentally friendly that I use it for another 5-10 years first before it will eventually be recycled, rather than it be recycled today. Reduce, re-use, recycle.

    I agree - battery recycling processes are still emerging as the industry is still quite young. One would think that battery recycling will have improved a lot in 5-10 years' time. I've seen a few companies starting to tackle Lithium Ion battery recycling, such as this one. Lithium as a raw material will likely remain quite valuable, so you would expect a big recycling industry emerge to capture that resale value. Though as an aside, I hope that simpler energy storage technologies take off which don't need rare earth materials. This one for example, using simple gravatational storage at huge scale.
    unkel wrote: »
    The current case for an SEAI scheme installed battery in Ireland with our massive extra subsidy for battery systems is marginal at best. Even taking into account a rise in electricity prices and expecting the battery to last longer than the manufacturer's spec sheet, pay back is in the region of 15 years. At best. Throw in a feed in tariff in the next few years, even a very low one of say 5c/kWh and installing a battery system now will lose you money, not make you any. But of course people can still do it for environmental reasons, as a hobby or if they can implement a battery system for far lower costs than a taxpayer subsidised battery system. I'm in all those 3 categories myself.

    This is a good point on the fact that the feed in tariff will effect the economics of home battery systems. It would seem like an unintended consequence however given Ireland's long term goals. Zooming out, a grid feed in tariff that disincentivises batteries doesn't solve the problem that to decarbonize the grid we'll need to: (1) Build lots of renewable energy generation capacity, solar on our roofs and otherwise (2) Build lots of energy storage to store renewables when they are generating for times that they are not. (1) is pretty straight forward. (2) is hard, and we will need to create incentives to build the something like 1,680GWh of storage (rough guess at what we'll need of 5GW * 14 days * 24 hours in a day) we'll need to store wind and solar for period of no renewables. A feed in tariff that disincentives adding distributed storage to our grid would be completely in the wrong direction so either that is changed at some point, or we fail in our decarbonization goals at great detriment to our collective future.
    Muahahaha wrote: »
    Great post Conor. Wondering might future building regulations make the installation of a battery mandatory?
    Yes, I would like to see this happen as we will need a lot of flexability in the system if we're to get to 100% decarbonised power. We're also going to see congesion on the Distribution Grid when people switch over to EVs in large numbers, which home batteries can help alleviate. However, some of the replies above make good financial arguements. We'll need better incentives to make batteries financially viable for everyone. Electric Cars will also represent a lot of flexability available to the grid if incentives are properly structured to allow people to get financial incentives to make their cars available to balance the grid, so if that was done properly, perhaps home batteries need not be manditory.
    Muahahaha wrote: »
    Must say I like the idea of filling up a battery on the night time rate for use during the day. But the cynic in me thinks if that became widespread the electricity companies would either abolish the night rate it or at least find a way of increasing it beyond the discounted levels. Much the way the govt. is going to have to come up with new taxes to replace losses on petrol/diesel as people move to EVs.

    The energy regulator sets electricity pricing for consumers in Ireland so I wouldn't worry about electricity companies in this regard. Electricity retailers just have the option to provide discounts on the regulated tariffs. As some others have mentioned here, the EU has targets first for SmartMeter roll-outs, and then to real-time pricing so that is coming down the line unless something major changes. Real-time prices should benefit people with batteries as there will be greater arbitrage opportunities. There are also emerging grid services markets where battery owners will be able to provide "flexibility" to the grid as get get up towards 100% renewables. That would essentially pay you to feed power into the grid at times of frequency issues, congestion in your local area due to EV charging, etc. I think that will actually be quite a big financial opportunity depending on how it is rolled out.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Conor20 wrote: »
    The environmental (e.g. Carbon reduction) benefit of SolarPV is that it reduces the need for fuel in some power plant when the solar is generating and hence lowering demand. ....

    So this is all just to say that it *when* you feed your power into the grid matters. If your solar generation coincides with the highest marginal CO2 intensity, then feeding it straight into the grid is better (from a CO2 perspective). However, if it doesn't, then it may prevent more CO2 emissions stored in a battery until a grid demand peak coindices with low wind and solar. If you only care about CO2 reduction, then it may also make sense to charge the battery at times of low emissions (usually times of high wind) and feed it back into the grid at times of low wind (and high emissions). Looking at the chart above, if you charged the 13kWh Tesla Powerwall at 150gCO2 / kWh (emitting 13 kWh * 150 gCO2 / kWh = 1.950 kg CO2 ) and then discharged it when the grid was emitting 500 gCO2 / kWh (preventing the release of 13 kWh * 500 = 6.5kg CO2), you would have a net negitive emissions impact of 6.5kg - 1.95kg = 4.55kg CO2. The average Irish person emits about 13,000kg CO2 per year for perspective. So if you managed to do this every day, you'd reduce your net impact by 4.55kg * 365 = 1,660kg CO2 a year. Lots of simplifications here, but just to give an idea of how time of use really matters with energy consumption and storage to optimize your emissions.

    I think you've missed a few key points and not really addressed my point at all.

    Your representation above is all about feeding into the grid at a time of high emissions to reduce that burden and then taking it back out during low emissions.... sounds great... but the thing is that wind and Solar is relatively easy for Eirgrid to forecast at a national level and they provide those figures in advance already on their website and adjust their generators accordingly in advance.

    You get the lower emissions either way. It doesnt matter if it reduces it from 500 to 450 or 200 to 150.... its still a 50g gain. I dont think your representation is accurate and certainly not practical as you can only charge/discharge a local battery as the sun shines and as you need it in the house... you cant really closely align it to any specific gCO2 figure from Eirgrid..... your needs as a human around your house take precedence.

    And crucially, you havent mentioned the emissions from creating the battery in the first place which is my primary point. Letting it go to the grid is more environmentally sound, imo.

    If you really want to support storage it is the like of Turlough hill and the new one they are creating in Tipperary that we need to support as taxpayers, not causing new Li-ion batteries to be mined from the other side of the world for questionable gain.

    Large scale grid level storage is what we need to look at and incentivise, not individual level storage... particularly Li-ion batteries which have a finite life. Turlough hill only had to be built once and is running for decades.

    Conor20 wrote: »
    This is a good point on the fact that the feed in tariff will effect the economics of home battery systems. It would seem like an unintended consequence however given Ireland's long term goals. Zooming out, a grid feed in tariff that disincentivises batteries doesn't solve the problem that to decarbonize the grid we'll need to: (1) Build lots of renewable energy generation capacity, solar on our roofs and otherwise (2) Build lots of energy storage to store renewables when they are generating for times that they are not. (1) is pretty straight forward. (2) is hard, and we will need to create incentives to build the something like 1,680GWh of storage (rough guess at what we'll need of 5GW * 14 days * 24 hours in a day) we'll need to store wind and solar for period of no renewables. A feed in tariff that disincentives adding distributed storage to our grid would be completely in the wrong direction so either that is changed at some point, or we fail in our decarbonization goals at great detriment to our collective future.

    As above, it needs to be large scale grid level, not private individuals UNLESS some new low impact battery tech appears... Li-ion is not it.

    Conor20 wrote: »
    Yes, I would like to see this happen as we will need a lot of flexability in the system if we're to get to 100% decarbonised power. We're also going to see congesion on the Distribution Grid when people switch over to EVs in large numbers, which home batteries can help alleviate. However, some of the replies above make good financial arguements. We'll need better incentives to make batteries financially viable for everyone. Electric Cars will also represent a lot of flexability available to the grid if incentives are properly structured to allow people to get financial incentives to make their cars available to balance the grid, so if that was done properly, perhaps home batteries need not be manditory.

    Again, I'd strongly disagree with your view here from an environmental perspective if its based on current battery tech.

    We should not incentivise batteries any further and governemnt policy is also against you in that regard as they have recently reduced the incentive for batteries and increased it for the panels.... which I agree with.

    What is needed is Vehicle-to-Home and Vehicle-to-Grid tech being developed and commercialised, not creating new batteries, which to be fair you have said in the latter half of your statement but you seem awful keen to get a battery installed anyway! :)

    V2H and V2G already exist and are catered for in current EV standards/protocols, we need to develop that technology not mine,create, install another Li-ion battery that has a finite life.


  • Registered Users, Registered Users 2 Posts: 19,688 ✭✭✭✭Muahahaha


    Conor20 wrote: »
    The energy regulator sets electricity pricing for consumers in Ireland so I wouldn't worry about electricity companies in this regard. Electricity retailers just have the option to provide discounts on the regulated tariffs. As some others have mentioned here, the EU has targets first for SmartMeter roll-outs, and then to real-time pricing so that is coming down the line unless something major changes. Real-time prices should benefit people with batteries as there will be greater arbitrage opportunities. There are also emerging grid services markets where battery owners will be able to provide "flexibility" to the grid as get get up towards 100% renewables. That would essentially pay you to feed power into the grid at times of frequency issues, congestion in your local area due to EV charging, etc. I think that will actually be quite a big financial opportunity depending on how it is rolled out.

    This is where the cynic in me kicks in. I just cant see a situation whereby the regulator allows someone to fill up at 9c/kwh at night and then sell back at 18c/kwh during the day.

    I think I read something a while back about the introduction of a feed in tariff. The sum mentioned was something like a payout of 5/6c kwh so only useful to people generating via solar and even then a bit of a slap in the face when the electricity providers can then sell that at the top prices of 18ckwh.

    Hope it runs differently of course but we have some of the highest electricity prices in the EU and I dont have confidence in the regulator that they will come down on the side of the consumer over the major power companies. I just feel 'this is Ireland', etc.


  • Registered Users, Registered Users 2 Posts: 9,814 ✭✭✭antoinolachtnai


    Muahahaha wrote: »
    This is where the cynic in me kicks in. I just cant see a situation whereby the regulator allows someone to fill up at 9c/kwh at night and then sell back at 18c/kwh during the day.

    I think I read something a while back about the introduction of a feed in tariff. The sum mentioned was something like a payout of 5/6c kwh so only useful to people generating via solar and even then a bit of a slap in the face when the electricity providers can then sell that at the top prices of 18ckwh.

    Hope it runs differently of course but we have some of the highest electricity prices in the EU and I dont have confidence in the regulator that they will come down on the side of the consumer over the major power companies. I just feel 'this is Ireland', etc.

    the price of electricity isn’t regulated. It’s set by the market.

    The wholesale price of renewable electricity on average is lower than the price mentioned. There is a lot more to electricity than just generating it. You also have to pay for distribution, transmission, imperfections and capacity.

    Many of the arguments here for not having home batteries distributed across the grid equally apply to home PV.


  • Registered Users Posts: 265 ✭✭Conor20


    KCross wrote: »
    I think you've missed a few key points and not really addressed my point at all.

    I'm not trying to dodge your point. I really do want to be kept honest on the maths here, so let me have another try! I take the main point of your reply is that batteries cause more Carbon in their manufacture than they prevent through emissions arbitrage, so let's take a stab at the numbers to see whether this is case. I'll take a stab at the math on the Carbon impact, while acknowledging there are other concerns about batteries on human rights where the metals are mined that are harder to measure.

    A 2019 Emissions From Lithium-Ion Battery Production report says carbon emissions from battery manufacture range from a low of 61 kilograms per kilowatt-hour to a high of 106 kilograms per kilowatt-hour. So a 13kWh Powerwall will release between 793kg and 1,378kg CO2. The manufacture CO2 footprint fell from 200kg / kWh in 2017, so presumably the mining and manufacturing footprint is on a downward trajectory. We need to figure out the emissions we can save with a battery to calculate the emissions "payback time" so see below for that.
    KCross wrote: »
    Your representation above is all about feeding into the grid at a time of high emissions to reduce that burden and then taking it back out during low emissions.... sounds great... but the thing is that wind and Solar is relatively easy for Eirgrid to forecast at a national level and they provide those figures in advance already on their website and adjust their generators accordingly in advance. You get the lower emissions either way. It doesnt matter if it reduces it from 500 to 450 or 200 to 150.... its still a 50g gain. I dont think your representation is accurate and certainly not practical as you can only charge/discharge a local battery as the sun shines and as you need it in the house... you cant really closely align it to any specific gCO2 figure from Eirgrid..... your needs as a human around your house take precedence.

    I think you would be surprised by how inaccurate forecasts for wind and solar generation currently are. Solar generation is ultra local - a cloud floating across the sky can temporarily decrease a solar farms production. Predicting PV generation with accuracy requires real-time geo-stationary satellite data coupled with ultra local knowledge of the location of PV farms. Wind generation is similarly difficult to predict at a local level as it is so influenced by minute changes in wind speed and direction and local topography. You can build a macro inference between weather and renewable generation and then forecast generation based on weather forecasts alright, but it is not accurate to the granularity it would need to be to remove the need for real-time balancing. Also, you would need to accurately predict demand to a similar granularity. Supply and demand need to be exactly equal or the frequency of the system drops or increases. If these were possible, we would only have a day ahead power market. But in reality, SEM-O who operate the power market in Ireland, implement a day ahead market, as well as a balancing market where some power plants are finely adjusted on a minute by minute basis such that generation exactly meets demand. This fine balancing can and does happen in response to changes you make to either increase or decrease your consumption and that is the reason that a battery does have an emissions impact. It has an emissions arbitrage between the marginal CO2 of the energy you stored in the battery (solar from your roof, which has a marginal CO2 intensity for each additional kWh generated of 0 gCO2) and whatever the marginal power plant is on the grid at that time. If that is a gas plant, that's about 400 gCO2 / kWh. If it's a coal plant such as Moneypoint, it is about 900g CO2 / kWh.

    There is a lot of research on this area, so you don't have to take my word for it. ElectricityMap are an NGO who analyse electricity markets in Europe in real-time to make available the 5-minute marginal CO2 intensity in gCO2 / kWh so that companies (or people like us) can optimize the emissions of electricity consumption. "When a consumer is asking for more electricity, that additional electricity will come from the cheapest power plant that still has spare capacity at that time. This power plant is called the marginal power plant. Typically the marginal plant is a system that can react quickly to changes in electricity demand, such as a gas turbine. It however cannot be a wind turbine or solar cells, as you can’t command them to produce more (unless you command the weather that is):

    marginalplantcurve.png

    As a consumer, when you decide to charge your electric vehicle at a given time, you are causing the marginal plant to produce more, and therefore, are responsible for the carbon emissions associated to it. Those emissions are called marginal carbon emissions. It is the quantity that should guide our choice as flexible consumers. For example, it is better to charge your electric vehicle when a hydro dam provides the additional electricity, compared to when a gas turbines does (as the latter has much higher emissions). Note that long-term effects exist (e.g. the depletion of a hydro reservoir that would causes coal plants to supply electricity once it’s empty), but we here focus on short-term effects."

    You can see where Ireland fits into Europe for our average marginal CO2 intensity, about 510gCO2/kWh :

    EuropeanMarginalEmissions.png

    So now we have the figure we need to calculate the emissions return of a Tesla Powerwall. Best case, it's manufacture released 793kg. Best case, we cycle it once per day charging it with solar and discharging it at the average marginal emissions intensity of 510gCO2 / kWh. That's 510g per kWh * 13 kWh so 510 * 13 = 6.630kg per day. So it takes 793kg / 6.630kg per day = 119.6 days for the battery to break even best case. Worse case, the manufacture releases 1,378kg CO2 and we can only manage to time our discharging to achieve say, 50% of the possible emissions arbitrage. So we save 6.630 / 2 = 3.315 kgCO2 per day in emissions arbitrage, and so our battery takes 1,378kg / 3.315 kg per day = 415.6863 days, or 415.6863 / 365 = 1.1 years to become Carbon negative.

    That's a useful range to have even if it is back of the envelope and best case - a stationary lithium ion battery in your house can become Carbon positive within a year, and is warrantied for 10.
    KCross wrote: »
    V2H and V2G already exist and are catered for in current EV standards/protocols, we need to develop that technology not mine,create, install another Li-ion battery that has a finite life.

    Definitely agreed that Vehicle to Grid is better than stationary batteries. Using a battery in an EV that would have manufactured anyway rather building another additional stationary battery is clearly best. But I think this will take longer to bring the amount of storage we'll need to be brought online at the distribution level through V2G to add the flexibility we'll need to get to 100% decarbonised electricity. EV manufactures are currently preventing V2G from materializing by removing warranties if cars are used in this way. I think it's a matter of time, but stationary batteries are available now and their specific purpose is for charge and discharge to and from the grid so they can fill the gap in the meantime.

    KCross wrote: »
    As above, it needs to be large scale grid level, not private individuals UNLESS some new low impact battery tech appears... Li-ion is not it. V2H and V2G already exist and are catered for in current EV standards/protocols, we need to develop that technology not mine, create, install another Li-ion battery that has a finite life.

    Yes, I agree that large scale storage, particularly pumped hydro is the best option for macro level storage of renewables to tide us over for a few weeks of low renewable generation. The solution(s) also have to address local distribution system congestion however - when everyone's charging their electric cars, and your local substation is maxed out, it doesn't matter if we have spare pumped hydro capacity in Tipparary at that moment, you can't get any more power through the substation. The extra power needs to come from *below* the substation. That is where local batteries can help deliver stored renewable power in a way that is cost effective - they remove the need to double the size of all of our substations in response to the inevitable roll-out of electric vehicles at a large cost to tax / electricity bill payers. That is why I think that incentivising home batteries is a good long term approach for us environmentally and financially. One part of the many solutions we'll need.


  • Registered Users, Registered Users 2 Posts: 3,412 ✭✭✭randombar


    Just to add to the arguments :D I agree grid storage would be very useful but another reason for me to have my battery storage is backups for power cuts, out in the countryside myself, prone to a few through the year. (More storms = more power cuts)

    Also on that, with the removal of fireplaces and the switch to A2W as your sole heating source for new builds I really think PV plus battery back up would be needed in the event of an extended powercut.


  • Registered Users, Registered Users 2 Posts: 15,104 ✭✭✭✭loyatemu


    GaryCocs wrote: »
    Just to add to the arguments :D I agree grid storage would be very useful but another reason for me to have my battery storage is backups for power cuts, out in the countryside myself, prone to a few through the year. (More storms = more power cuts)

    Also on that, with the removal of fireplaces and the switch to A2W as your sole heating source for new builds I really think PV plus battery back up would be needed in the event of an extended powercut.

    isn't there some issue with using the batteries when the grid is down - thought it had been mentioned earlier in the thread.


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    loyatemu wrote: »
    isn't there some issue with using the batteries when the grid is down - thought it had been mentioned earlier in the thread.

    In a typical setup you can use the batteries when the grid is down, but you can't charge them up with solar PV, so once they're empty, that's it

    That said, with a typical say 5kWh battery, this is enough to power some basics like phone chargers, wifi router, bulbs and tv for several days


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  • Registered Users, Registered Users 2 Posts: 1,891 ✭✭✭SlowBlowin


    loyatemu wrote: »
    isn't there some issue with using the batteries when the grid is down - thought it had been mentioned earlier in the thread.

    An issue with grid connected systems is ensuring there is no feeding into the grid when engineers are working on the line.

    I believe the latest Tesla PWs are capable of switching between no grid and grid, not sure of the regulations in Ireland though.

    My system is in parallel to the grid so I am OK.


  • Registered Users Posts: 138 ✭✭kennypowers


    unkel wrote: »
    In a typical setup you can use the batteries when the grid is down, but you can't charge them up with solar PV, so once they're empty, that's it

    That said, with a typical say 5kWh battery, this is enough to power some basics like phone chargers, wifi router, bulbs and tv for several days

    novice question but why wouldnt your solar pv be able to recharge some of your battery? I live in an area that gets numerous power outages a year and as a result have become interested in getting pv as a supplement when this occurs.


  • Registered Users, Registered Users 2 Posts: 2,555 ✭✭✭wexfordman2


    novice question but why wouldnt your solar pv be able to recharge some of your battery? I live in an area that gets numerous power outages a year and as a result have become interested in getting pv as a supplement when this occurs.

    Technically, it is absolutely possible, but regulations do not permit it. In the event of a power cut from the mains, all solar production must be automatically disconnected, and the pv system disconnected from the mains.

    It is not even permitted to discharge the remaining capacity of your battery into the mains of the house,.if you wish to use up your battery capacity during a power outage, it must be via a dedicated and completely isolated circuit from the mains.

    All to do with fire regulations and safety of esb personal working in power lines outside of your house.


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    If you do have regular grid blackouts that have a bad impact on your household, you could consider an off grid system.


  • Registered Users, Registered Users 2 Posts: 1,891 ✭✭✭SlowBlowin


    You don't need to do it all at once.

    In my layout the workshop is on the side of the house, so initially I put the batteries in the workshop and powered the lights and the fridge freezer which were in the workshop. I also had my internet/wireless stuff in there so when we had a power cut we had Internet and a working fridge, as well as USB chargers etc. That was a good phase 1, then as I added PV capacity I added a feed into the house, totally independent of the existing wiring system.


  • Posts: 7,499 ✭✭✭ [Deleted User]


    SlowBlowin,

    What would you recommend for getting some solar EV charging going?
    Or where to find more info.
    I have a zappi charge point .

    Cheers


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  • Registered Users, Registered Users 2 Posts: 1,891 ✭✭✭SlowBlowin


    SlowBlowin,

    What would you recommend for getting some solar EV charging going?
    Or where to find more info.
    I have a zappi charge point .

    Cheers

    Hi

    Not having an EV (other than the bike) I am probably not the best person to ask. Have you seen the episode of fully charged where they use a Zappi on solar ? That would be a good starting point.

    Unkel has a solar install and an EV, I bet hes done some research.

    From the technical perspective, there is talk that trickle charging (granny cable) can shorten the lifespan of some battery packs, so a system with stationary battery that charges, then dumps into the car at a higher rate is preferred. The trouble is that cars charge at tremendous rates, and most home PV systems are only capable of charging at limited rates. As I said I have no knowledge of this and Unkel is probably better placed to comment, but do watch that episode of Fully charged if you can, they have the MD of Zappi on.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    SlowBlowin wrote: »
    From the technical perspective, there is talk that trickle charging (granny cable) can shorten the lifespan of some battery packs,...

    I've never heard that and I doubt its true.

    Its high rates shorten the life span, not low rates.


  • Registered Users, Registered Users 2 Posts: 1,891 ✭✭✭SlowBlowin


    KCross wrote: »
    I've never heard that and I doubt its true.

    Its high rates shorten the life span, not low rates.

    Yes you are most likely correct, it was something I "heard" that using granny 100% can lead to some issues.

    In my experience, as you said, its always the other way round. It might a miss quote and they were referring to the poor efficiency of the granny cable vs a faster charger..


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    SlowBlowin wrote: »
    ...they were referring to the poor efficiency of the granny cable vs a faster charger..

    That is true.

    The car chargers are usually optimised for 16A or 32A charging so charging it at 10A tends to be less efficient. Maybe instead of it being 90-95% efficient it is now closer to 80% efficient.


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    What would you recommend for getting some solar EV charging going?
    Or where to find more info.
    I have a zappi charge point .

    That's good. The only thing you need then is to install a PV system. The Zappi charger can send all electricity that you produce more than you are consuming, to the car. Provided of course the car is plugged in.

    I would recommend you go for the biggest system you can afford and will fit on your roof. At the very least 3kwp. The bigger the system, the cheaper per watt installed it is. And once it's on the roof, you won't really have to worry about it ever again.


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  • Registered Users Posts: 265 ✭✭Conor20


    (I had to split this post into several posts as I was having trouble linking from external images, and had to use attachments which have a limit of 5)

    I started this project five years ago with a simple question: how can I provide for my children's future, whilst ensuring they have a future? That means finding a solution for life that's reconciled with climate change, but in a way that creates wealth and positive returns. Technologies have done us all favors in this regard and I found myself investing in a few simple measures early on that allowed us to save for bigger changes, which saved more money. We saved as much of those savings each month as we could so we had a pot of money that was growing increasingly quickly with money we otherwise would have just spend on light, heat and transport. They were things like replacing our petrol car with a second hand electric car, cycling rather than owning a second car, installing double/triple glazed windows, installing LEDs throughout the house, and adding attic insulation.

    Six months ago, we took these accumulated energy savings and invested in achieving a low energy cost household. We wrapped the house in insulation, we switched the heating from gas heating to an electric heat pump, and we installed a 5.8 kW Solar PV array. Additionally, we replaced the gas cooker hobs with electric induction hobs (Ikea sell them starting at €39) to fully remove gas bills from our house forever. We had already switched to an electric car from our old petrol car. Our house now requires a lot less heat, that heat comes from an electric heat pump, and for a lot of the year, that electricity comes from Solar panels on the roof.

    All of this is in a bog-standard 1980s three bed semi-d originally built with minimal thought to running costs. If we can do it, anyone can. Five years ago, our energy costs across our car, heating, hot water and electricity totaled €4,703.56 per year. Now they total €778.13 a year.

    Had we changed nothing and continued with our 2015 baseline, over the next 10 years we would have spent €47,035 on the energy required for our lives. Instead, with the changes we've made, we'll spend €7,781, freeing up €39,254 and giving us a lot more financial stability. One of the key lessons we've taken from the unpredictable nature of the last two years is that finding ways to earn more money is really hard, and when you do, you pay a lot of those increased earnings in tax. We've realized it's a hell of a lot easier to spend less money that it is to earn more, and the net effect on our cashflow is the same.

    SolarPV
    We had already installed a 2.5kW SolarPV system on the front of our house three years ago, but as we now are heating our house with electricity, and powering our car with electricity, I saw it as a financially positive investment to increase the size of our SolarPV system to 5.9kW by adding extra panels on our flat back roof.
    536656.jpg

    Our day rate is €0.1874 and our night rate is €0.927. Our SolarPV system generated 1850kWh of electricity in the first 4 months of operation, but this was spring and early summer. Based on previous data from the smaller SolarPV system we had, year round, it will generate 4,260 kWh per year. The battery soaks up almost all export, but I think we'll export about 250 kWh per year, mostly during stretches of long blue-sky days in May/June. That leaves 4,260-250 = 4,010 kWh per year that we'll consume, offsetting the need to pay for it. Taking a simple day rate calculation for the value of this electricity is €0.1874 * 4010 = €751.474 per year. The figure is more complicated for two main reasons:
    (1) Detracting from this net impact cost, some of the electricity consumption the SolarPV offsets, we would otherwise have consumed at night rate (€0.927). I estimate this to be about 50%. So (4010 * .5 * €0.1874) + (4010 * .5 * €0.0927) = €561.60. The SolarPV system cost €5,198 after the €1,950 grant so the yearly ROI is €561.60 / €5,198 = 10.8% . It's warrantied for 20 years, so the full payback of investing in solar will be in the region of 561.60 * 20 = €11,232. Higher if energy prices go up, which they are very likely to do.

    (2) If your original baseline is a petrol or diesel car, and you switch to solar, putting the solar generated electricity into an electric car would save more as it is saving money you otherwise would have been spending on petrol. A litre of Petrol contains 12.8889 kWh, burned in an internal combustion engine with a max. efficiency 38%, so your €1.26 litre of petrol gets you about 4.8kWh, or €0.2625 / kWh. So if you're doing calculations on making a big switch to cut costs in your life by switching to SolarPV + an Electric Car, and you put 2,000kWh of solar into your car, that will give you an extra bonus saving of 2,000 * €0.2625 = €525.00 ( 2,000 * €0.1874 = €525- €374.8 = €150.2

    Here's a day in May - solar generated 23.7kWh of electricity. We consumed 21.9kWh of that between powering the house, heating water in the hot water tank via the Heat Pump, and the excess went into the battery. The electricity stored in the battery continued to power energy consumption of the house after the sun went down. So of the total of 21.9kWh we used that day, we imported only 2.7kWh from the grid. Our electricity bill in May was €15.18 - it's quite remarkable to me that on sunnier months like this, we can power our house, transport and heat almost entirely from solar.
    536658.png

    If you're working out a solar installation for your house, the SEAI grant will pay you €3,000 for a 4kWp system with a battery, €2,400 for a 4kWp system with no battery, and €1,800 for 2kWp system of about 8 panels. This would fit within the 12m^2 size which requires no planning permission even if it's on the front of your house. Also, the Irish government are mandated by the EU to introduce a feed in tariff scheme by the June 2021, so people with SolarPV installations will be paid for excess electricity back to the grid.


    Battery
    The battery saves money in two ways: in summer, it stores excess solar which would otherwise have been exported. Looking through the summer figures, the resultant stored solar we used about two third of the time during the day rate (€0.18 kWh) and about a third during the nighttime (€0.09 / kWh). We stored an average of about 5 kWh per day over those 6 months - maxing out the 8.2kWh of storage almost every day during May, June and July, and averaging about 3kWh a day in April, August and September. That translated to a saving of 6 * 30 * .66 * 5 * €0.18 = €106.92 +
    6 * 30 * .33 * 5 * €0.09 = €26.73 . So €106.92 + €26.73 = €133.65 per year in the summer months for the battery.

    Secondly, in winter, we can charge it at the night rate (€0.09) and use it to power the house to avoid the day rate (€0.18), saving €0.09 per kWh. We do this for the 6 less sunny months of the year, offsetting 8.2kWh of daytime consumption every day, so saving 6 winter months * 30 days per month * 8.2kWh * €0.09 / kWh saving = €132.84 per year.
    536659.png

    The battery thus saves €133.65 + €132.84 = €266.49 per year. The battery's net cost was €1900 which gives a 1900 / 266.49 = 7.1297 year payback of the battery, or a 14% yearly return (266.49 / 1900) if the full cost of the battery is written off at the end of the 7 years.

    So, right now the battery is not a positive investment. It may be in the future when homes are rewarded for providing flexibility to the grid. It does also provide one other thing however - continued power in the event of a grid blackout. The SolarPV and battery inverter system comes with a power back-up connection which provides a power outlet which will continue to work if the grid goes down. The SolarPV system continues to work with the battery, but not the rest of the house or the grid which is a legal requirement. This means that if the grid goes down, we can continue to power key appliances and the car indefinitely with solar in the event of a prolonged grid blackout. 

    536660.jpg

    Insulation
    Insulation is not the most exciting of things to do but it is by far the most important of anything listed here. Before installing SolarPV or a Heat Pump, your house should be really well insulated. A few years ago, we replaced all of our windows with double glazed windows, installed a new airtight front door to stop drafts and insulated the attic. This time we finished the job. We wrapped (e.g. installed external insulation) on the side and back of the house, and installed internal insulation on the rooms at the front of the house (as modifying the front of the house would have required planning permission). The insulation cost €9,300 with the €4,500 SEAI grant, but it has utterly transformed the house from a drafty cowboy build three bed semi into a warm and cozy house that stays at a constant temperature which will require drastically less energy to heat it for the next 50-60 years of its lifespan. It used to be like a leaky bucket into which we had to constantly pump heat (e.g. money) into to keep heated. Now it's cozy and warm through winter without requiring much heat input to keep it that way.

    Heat Pump
    A heat pump is quite a miraculous machine. Other heating systems, such as gas boilers, wood stoves and oil fired boilers are 50-80% efficient. That is to say 50-80% of the energy you put into them in the form of fuel comes out as useful heat. Heat Pumps can be 200-400% efficient by virtue of that fact that they are not creating heat, they are simply pumping it in from the outside. For every one watt of electricity you power the Heat Pump with, it delivers 2-4 watts of heat into your house. The result is a heating system which is incredibly energy efficient. Couple it with a SolarPV system on your roof and when the sun is shining, you have ultra-efficient, completely free heating and hot water.

    Heat Pumps work the same way that a fridge does, but in reverse. A fridge has a loop of piping that runs inside and outside of the fridge. It uses a valve to compress a fluid inside the pipe inside your fridge. As the liquid becomes more dense, it sucks in heat from the air cooling down the air in the fridge. A pump keeps the fluid moving around the loop. Another valve outside the fridge expands the liquid, and as it expands, it can hold less heat, so it dumps the heat it absorbed inside the fridge outside the back. This keeps the fridge cool inside. A heat pump heating system is exactly the same but in reverse. It uses two valves and an electric pump to pump a liquid around in a loop.

    The Heat Pump we installed is a Hitachi R32 Yutaki-SCombi 2 5HP 200L. The Coefficient of Performance (unit of heat energy out / unit of electrical energy to power it) varies with a few factors, such as the outside temperature and the temperature you are heating water to. For 35C water, the CoP varies from 2.7 (outside temp of -7C) to 8.35 (outside temperature of 12C). For 55C water, it goes from 1.85 (-7C outside temperature) to 6.35 (outside temp of 12C). It's listed with an all up CoP of 4.4 here. This is the full CoP table and other specs of the system:
    536661.png

    So that means for every 1 watt of electricity our heat pump consumes, it's pumping 4.4 watts of hot water into the hot water tank, or out into the radiators.

    [Continued in next post]


  • Registered Users Posts: 265 ✭✭Conor20


    [Continued from above]

    The Heat Pump consists of a fan unit which sits outside, a fridge-sized inside unit that sits inside (replacing the gas boiler), and a 200l hot water tank. The water tank will replace an immersion hot water tank, as it does the same thing with 25% of the electricity. We mounted the fan unit up on the side of the house so it was out of the way:
    536662.png

    Since installing the heat pump in March of this year, we have never run out of hot water - that includes showers, baths for the kids, washing and general usage all day while we were home during the lockdown, so I would say we have well and truly tested the capacity of the system and it's come up trumps.

    We installed underfloor heating on the ground floor and this results in a more efficient use of the heat pump. It allows us to run the heat pump to store heat in the floor of the house during the night or when there is excess solar generation. The floor stores a lot of heat and releases it slowly, so it will effectively heat the house for days. Underfloor heating is surprisingly simple - basically, put down insulation, put down a big loop of pipes and pour two inches of concrete on top:
    536669.jpg

    Underfloor heating isn't essential however. Two households we know have recently switched over to Heat Pumps from gas and oil heating respectively, without underfloor heating. They did change their radiators to Heat Pump radiators which are more effective at distributing heat. We installed these upstairs replacing the old rads:
    536664.PNG


    One other attribute of a heat pump, though we'll probably never have need for it, is that if it gets too hot in summer, a heat pump can run in reverse and act as air conditioning to cool down the house. I asked the installer about this and it does require the addition of a "condensation kit" to deal with condensing water if you put it into cooling mode, which costs about €500 to add. Still, might be useful if summers get a lot warmer in the coming years.

    Emissions
    Driving our petrol car used to release 2,600 kgCO2 per year. Switching to an electric car reduced that by 1,630 kg CO2 per year to 970.9 kg CO2. But looking back at my maths on that - before we installed SolarPV, we were charging it year round with electricity from the grid. A few things have changed that for the better since:
    1. The electricity grid in Ireland, like most countries around the world, has continued to go green, adding a lot of renewable energy capacity in the last 5 years and retiring several coal and turf power plants. It's now mostly renewables and gas.
    2. In summer, we are no longer charging our car from the grid, which has an average emissions intensity of 389 gCO2 / kWh, we are charging it from our SolarPV, which have an emissions intensity of about 18 gCO2 / kWh (this is the emissions released during their manufacture and transport divided by all of the kWh they will generate in their lifetimes). Because we installed an 8.2kWh battery, even if the car isn't plugged in during the day, we can that much solar into it via the battery in the evenings, which amounts to about 50km in an older Leaf.
    3. As renewables installed in Ireland is mostly wind, and it's windier in the winter in Ireland, that means the grid releases much lower CO2 per kWh in winter than it does in summer on average. Renewables average 37% in the winter months, with an average CO2 intensity of about 270g/kWh.

    So this means that we now charge our car for six months with an average of 270gCO2/kWh and the other six months with an average emissions of 18 gCO2 / kWh. We drive about 300km per week, which consumes 48kWh of electricity. So the net emissions are 48 * .270 * 4 * 6 = 311.04kgCO2 (6 months of winter) + 48 * .018 * 4 * 6 = 20.736kg CO2 (six months of summer) . So our driving is down to 311.04 + 20.736 = 331.776kg, a whopping 2,268.224kgCO2 reduction on our old petrol car. It also shows that as time goes on, and grid is increasingly powered by renewables, electric cars will get cleaner and cleaner.

    The installation of our heat pump has also removed all gas that we used to burn. We used to spend €793 a year on gas at €0.09 / kWh. So we used roughly €793 / €0.09 = 8,811.11 kWh of gas yearly. Gas emits .23kg CO2 per kWh from a gas boiler with reasonable efficiency, so our gas usage was emitting 8,811.11 * .23 = 2,026.55 kg CO2 every year.

    We used to need 8,811.11 kWh of gas to heat the house, which implies we consumed about 7,048.88kWh of heat yearly in the house given a boiler efficiency of about 80%. However, we now have the house fully wrapped in insulation and the BER inspection rated the heat consumption of the house at 57.5 kWh/m/year. The house is roughly 80M^2, which gives a yearly heat consumption of 57.5 kWh/m^2 * 80m^2 = 4,600kWh. So the insulation reduced the heat consumption of the house by about 2,500kWh per year (7,048.88 - 4,600 = 2,448.88 kWh reduction).

    Our Heat Pump, with a coefficient of performance of 4.4 delivers that 4,600 kWh of heat required by the newly insulated house with 4600 / 4.4 = 1045.4545 kWh of electricity. I'll use the same grid and solar CO2 intensity above, and I'm guessing we use about 66% of the heat & hot water in the winter months when it's powered by the grid, and 33% of it in the summer months when it's powered by solar. So that gives 1045.4545 * .66 * .27 = 186.3 kgCO2 (winter months) + 1045.4545 * .33 * .018 = 6.21 kgCO2 (Summer months) = 192.51 kg CO2 in total for our heating and hot water year round.

    So heating our house with gas emitted 2,026.55 kg CO2 every year, and the Heat Pump + Insulation + SolarPV combo heat the house emitting 192.51 kg CO2 per year, giving a reduction of 1,834.04 kg CO2 per year. So a pretty significant saving of 1,827.83 * 20 = 36,556.6 kg CO2 over the next 20 years.

    The Financial Impact all up
    Calculating everything requires having a baseline to compare against. I looked back to see what we were spending on energy before we started this whole process. That looked like this:
    536667.png

    It was costing us €3250.56 a year to run our petrol car (including maintenance and tax, both of which decreased considerably with the switch to the electric car). It was costing us €793 per year to heat the house with the gas boiler. Both of those bills have now disappeared. Our electricity bill was originally €660. So our combined energy and transport costs were €4,703.56 per year. Everything runs on electricity now - our power, transport, heating and hot water, and we generate most of that electricity ourselves with the Solar panels for part of the year. All of these bills combined look like they will come in at €778.13 this year. So these combined measures of Insulation, switching to an electric car, switching to a heat pump and installing SolarPV will reduce our costs by €3,925.43 a year.

    The totals for the work came to €24,898 after the grants. We availed of a pretty significant €10,550 of grants from the SEAI (see here). Looking at the numbers so far, a conservative estimate is that the changes will pay for themselves in 9-10 years. The SolarPV system is warrantied for 20 years. The Heat Pump is warrantied for 10. The insulation is warrantied for 20 years with a life expectancy of 30. I'll do a more comprehensive analysis of the payback when I have a full year of data (and more time!) but I think this is a solid investment. Particularly given the increase in quality of life you experience with a fully insulated house, and the daily buzz of seeing solar panels on your roof print money for you.

    The BER of our house has gone from D1 consuming 236.42 kWh / sqm / year to A3, consuming 57.5 kWh/m/year.
    536668.png

    I would just reiterate that when we moved into the house 6-7 years ago, the wind literally blew through it. Single glazed windows, no insulation at all, a front door which used to let the wind and rain in.

    I think why I value these changes so highly is that it's really difficult to earn more money. And when you do, you pay tax on those earnings. It's much easier to reduce your costs. So seeing our energy costs fall by €3,925.43 every year into the future removes a lot of stress about money, and makes it much more realistic for us to consider one or both of us retiring early if we want to.

    A note on the upfront costs of this work - we were lucky to have been able to save up the cost of these works by pretty relentlessly setting aside all of the savings from our previous changes. Not everyone will be able to get this money together and so I hope this is reflected in how the government support lower income households. It strikes me that retrofitting insulation, heat pumps and SolarPV as a much more helpful way to help people than a winter heating allowance for fuels which leave the household broke again next winter. Getting rid of the bills entirely would free up households from this repetitive treadmill, as well as keeping more money in the country that currently flows out to countries who export fossil fuels.

    I'm also aware that not everyone has enough time or interest to run complex numbers, so I will make some broad summaries that I think will be true for most people:
    • Insulate your house. I know it's boring but just to it. It will sit there saving you money for the next 30+ years and will make the house much more pleasant and cozy. There's an SEAI grant of €4,500 for wrapping your house.
    • Switching to an electric car, particularly a second hand EV, will save you a lot of money in the long term in fuel, maintenance and tax costs
    • For a family household, SolarPV is a good investment, better than just paying down your mortgage. If you consume little electricity, and there remains no feed-in-tariff, it may not be. But for most people it now is a financially positive investment. You can get an SEAI grant of €3,000 for installing SolarPV, and there will almost definitely be a feed in tarif by June 2021, as the EU begin fining Ireland for not having one by then. If you don't have an electric car or Heat Pump, install about 2kW. If you do have a Heat Pump and EV, it's worth installing up to 6kW of capacity if you have space.
    • If you switch to a heat pump to heat your house, that will both save you money, and allow you to make further savings from a SolarPV system
    • If you switch to an electric car, and install SolarPV, that will allow you to make further savings from SolarPV

    So there you have it. If you want to permanently lower your energy costs into the future, I recommend insulating your house, switching to an electric car, installing SolarPV, and heating your house with a Heat Pump.


  • Registered Users, Registered Users 2 Posts: 365 ✭✭Gerard93


    Thanks Conor20 for such a detailed post fantastic what you have achieved... now I have to read it all again !!


  • Registered Users, Registered Users 2 Posts: 1,891 ✭✭✭SlowBlowin


    I just think this post is beautiful in its construction and detail, I have not fully digested the content but I have no doubt that's fantastic too. I need to read it a few times, but what a project, love it, good job !


  • Registered Users Posts: 861 ✭✭✭tails_naf


    That's a brilliant result Conor20, really shows what can be done, and that going green is viable. Regarding the heat pump, is it fair to say with the cost of a unit of oil being around 6 or. 7 c per kwh, you need a CoP of at least 3 to break even with a heat pump using day rate units, or do you only let it run at night? I have oil at the moment, about 1600l a year, which is around 750 euro at the moment, so hard to see switching to air to water as being cost effective for me.


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    Gas is well under 5c/kWh (including VAT and carbon tax), so a lot of heat pumps will be more expensive to use if you use 24h electricity rates. Would be stupid to still be on a 24h rate if you have a heat pump (or an electric car for that matter)

    Also the cost to switch is very material, heat pumps are expensive, even after subsidies. And from anecdotal evidence they don't seem to be very reliable compared to good old oil / gas boilers and when they break they seem harder to fix with fewer people around to fix them. But that can of course be attributed to the fact that we are adapting newer technology and we are in a change phase. Few car mechanics will be able to fix a high voltage battery problem with a Nissan Leaf either :D

    Heat pumps will also only work in very well insulated housed

    Of course you will lose your gas / oil bill and any standing charges or delivery costs. And stop using fossil fuels. The grid is getting cleaner every year, so using electricity for heating (particularly at night) is a major step in the right direction


  • Registered Users, Registered Users 2 Posts: 33,987 ✭✭✭✭NIMAN


    This is a very interested thread but there is an awful lot of data and info in it for someone who has just discovered it.

    @op, do you have an overall figure for
    (1) how much you have spent in changing your house/lifestyle etc to be more energy efficient, minus grants
    (2) savings youhave made so far by doing so

    I appreciate its a long term project and will pay back over the rest of your life, but curious as to how much it would cost the average person to being making these types of changes?


  • Hosted Moderators Posts: 23,145 ✭✭✭✭beertons


    That's class. Have to sit down with a coffee layer and read it in entirety.


  • Registered Users, Registered Users 2 Posts: 12,136 ✭✭✭✭KCross


    Conor20 wrote: »

    SolarPV
    We had already installed a 2.5kW SolarPV system on the front of our house three years ago, but as we now are heating our house with electricity, and powering our car with electricity, I saw it as a financially positive investment to increase the size of our SolarPV system to 5.9kW by adding extra panels on our flat back roof.

    (2) If your original baseline is a petrol or diesel car, and you switch to solar, putting the solar generated electricity into an electric car would save more as it is saving money you otherwise would have been spending on petrol.


    Fair play on all the works you have done.


    EV/Solar integration
    Looking at your pictures it looks like you have a standard Rolec charge point and you said a Leaf. How do you manage the flow of electricity from the Solar to the car in that case as it will be pulling a constant 3.6kW for hours and not reacting to when clouds roll in or other appliances fire up thus causing you to unnecessarily pull expensive day rate electricity.

    It would typically require a Solar integrated smart charge point to manage that automatically. Are you doing it manually? I know your battery helps too but that still wouldnt cover it.

    Are you manually checking a monitor to see if there is 3.6kW of excess Solar and then plugging the car in/out accordingly?


    Heat pump
    How noisy is that outside unit? I hear alot of complaints about noise from those units when they are running at full tilt. Being tied directly to your outside wall is also not typically recommended as it can cause vibration through the walls. Usually they are on an independent foundation on the ground but I can see why you would mount it high to get it out of your way. Any complaints from the neighbours on the noise? Any noise inside your own house from it?


  • Registered Users, Registered Users 2 Posts: 19,688 ✭✭✭✭Muahahaha


    Excellent post Conor. Agree with you 100% on the heat pump, I replaced 25 year old storage heaters with an air to air HP last year and between that, new windows and some internal insulation on a north facing wall I saw an immediate drop in electricity bills. From memory October-Nov 2018 was 253 euro and then the same period in 2019 was 156 euro. Regarding the air conditioning function it is rarely needed in Ireland but when it is by god it is nice to have it. Arrived back to the house a few days last summer and it was sweltering inside at 27c with no breeze so it was great to be able to run the air con for 20 minutes and get the temperature down to 18. The unit I have is a Mitsubishi and it also has functions as an air purifier and a dehumidifier, it has an app as well to monitor kwh usage or turn it on over wifi when you are out of the house.

    Just on the external insulation, you said it is done on the gable side and back side of your 3 bed semi. How were the SEAI with this in terms of the grant, I had thought they only pay out if all sides of the house are completed? Also did any energy assessor say that it would be less efficient if not fully wrapped or talk about cold bridges? And can you recall the cost of the EWI per sqm? I had got quotes for it before and from memory it came to about 150sqm so not a small cost. In my own situation Id would like to do the gable side of the house which is often cold but as far as I know the SEAI wont give the grant for only one side so Id have to pay the entire cost myself.


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  • Registered Users, Registered Users 2 Posts: 1,213 ✭✭✭FionnK86


    What an achievement Conor. I wish I'd money to buy my own place. Landlord not accepting proposals to improve the house as we're footing the energy bills.


  • Moderators, Sports Moderators Posts: 19,192 Mod ✭✭✭✭slave1


    Nice post and thanks for the carbon reductions.

    Perhaps a small point but in Winter when you are charging the battery at night, that electricity is mostly renewable generation versus not charging up the battery and using non-renewable at say midday lunch. So it's not just a financial saving, it's a carbon saving too.
    Charging your battery at night in Winter will probably result in about 10% electric loss and another 10% loss when discharging during the day, again small point.
    Perhaps it's buried in your assumptions.

    Well done again


  • Registered Users, Registered Users 2 Posts: 1,460 ✭✭✭Evd-Burner


    I've been following this a long time and have I have implemented a few the items you have with a plan to implement more

    Next item on my list when I can get the moment together is external insulation the back and gable wall. I have already had the front cavity pumped and front internal plasterboard pumped which made a huge difference. I'm just not sure how the grant works with just doing the gable and back.


  • Registered Users Posts: 265 ✭✭Conor20


    tails_naf wrote: »
    That's a brilliant result Conor20, really shows what can be done, and that going green is viable. Regarding the heat pump, is it fair to say with the cost of a unit of oil being around 6 or. 7 c per kwh, you need a CoP of at least 3 to break even with a heat pump using day rate units, or do you only let it run at night? I have oil at the moment, about 1600l a year, which is around 750 euro at the moment, so hard to see switching to air to water as being cost effective for me.
    unkel wrote: »
    Gas is well under 5c/kWh (including VAT and carbon tax), so a lot of heat pumps will be more expensive to use if you use 24h electricity rates. Would be stupid to still be on a 24h rate if you have a heat pump (or an electric car for that matter)

    Thanks! I spent a day thinking about this to try find the right measurement to directly compare gas and a heat pump from a cost perspective. Because the efficiencies are so different, the input costs don't really make sense to compare. When heating your house, the thing that actually matters is the cost of delivered heat, so I think the right measure for us to compare is € / kWh of delivered heat. If you can get gas for €0.05/kWh with a gas boiler with an efficiency of 80%, then your cost of delivered heat is €0.05 * (1/0.8) = €0.06 / kWh of delivered heat. If Oil costs about €0.07/kWh, then it will similarly cost about €0.08 / kWh of delivered heat.

    We next need to work out our average cost of electricity for the Heat Pump. So a quick delve into the cost of electricity from the SolarPV array. It generates 4,260 kWh per year, warrantied for 20 years, 4,260 kWh * 20 = 85,200kWh over it's warrantied lifetime, €5,198 / 85,200kWh = €0.06 / kWh. I would say we're powering the Heat Pump with a mix of SolarPV, Night Rate electricity and day time electricity roughly equally, so the average electricity cost for the Heat Pump is - ( (€0.06 * .33) + (€0.08 * .33) +(€0.19 * .33) ) = €0.11 / kWh on average.

    For a heat pump with an efficiency of 440% (e.g. a CoP of 4.4 meaning for every 1kWh of electricity it consumed, it pumps 4.4kWh of heat into your house), at an electricity cost of €0.11 / kWh means €0.11 * (1/4.4) = €0.03 / kWh of delivered heat.

    So a heat pump is roughly half the cost to run, at €0.03 / kWh of delivered heat, to gas at €0.06/kWh of delivered heat or to oil at €0.08 / kWh of delivered heat.
    unkel wrote: »
    from anecdotal evidence they don't seem to be very reliable compared to good old oil / gas boilers and when they break they seem harder to fix with fewer people around to fix them. But that can of course be attributed to the fact that we are adapting newer technology and we are in a change phase. Few car mechanics will be able to fix a high voltage battery problem with a Nissan Leaf either :D

    Heat pumps will also only work in very well insulated housed

    This was certainly true a few years ago but there are huge new estates surrounding us and every house in them are fitted with heat pumps, so I think Heat Pumps are common enough now that most plumbers have already or will soon skill up on installing and maintaining them. Heat Pumps have been in widespread use since the 80's/90's in Scandinavia so I wouldn't be too worried about parts not being available. Yep - you need a well insulated house for sure. People should see Insulation + a Heat Pump as being the one job. The SEAI grants do soften the blow a lot though, with €4,500 for insulation (€6,000 for a detached house) and €3,500 for installing a Heat Pump.


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    Modern condensing oil and gas boilers are much higher efficiency than 80% though. And I have my doubts if a heatpump can really deliver a COP of 4.4

    But yeah, tune that down a bit, tune up the efficiency of the boilers in your calculation and take night into account (try to minimise running the heat pump during the day) and your conclusion still stands

    The calculation of the help from solar is flawed though. Most solar PV is not directly used (but sent to the grid, stored in an electrical battery or hot water storage) and when you need it most for your heatpump, none is available :p


  • Registered Users Posts: 265 ✭✭Conor20


    NIMAN wrote: »
    @op, do you have an overall figure for
    (1) how much you have spent in changing your house/lifestyle etc to be more energy efficient, minus grants
    (2) savings you have made so far by doing so
    This reply turned into a post in it's own right. Anyway, here we go! I've made some approximations here but this is the rough sequence by which we've tried to get off of the treadmill of energy costs! -->
    • Bought an energy monitor so we can see what's consuming and costing us what in 2013
      • Cost: €50
      • Savings: €1,000. The €1,000 is a complete guess but it made us way more energy aware as we were before and we pretty much immediately started being more efficient. It became fun to be efficient as we could see what we were saving whereas before, it felt like depriving ourselves for no reason
    • Switch to a Day / Night rate electricity meter and tariff in 2014
      • This is free to do and I recommend doing it. I think you just need to ring your electricity supplier and ask to switch to a day/night rate. You can then run appliances, charge your electric car, etc. at night at a much cheaper rate. We were able to save about €200 a year with the night rate meter before we switched to the electric car, and as soon as we switched to the electric car, it was saving us about €400 a year.
      • Cost: free
      • Savings: About €1,500 since 2014
    • Changed all light bulbs to LEDs in 2014:
      • Cost: €100
      • Savings: 495.165 kWh per year | €87.29 per year | 274.8697 Kg CO2 per year. So in 6 years, it's saved us 87.29 * 6 = €523.74 so far for the €100 invested, so €523.74 - €100 = €423.74 in profit
    • Bought an electric bike in 2015 and used it as a way to avoid having a second car until 2020:
      • Cost: €750
      • Savings: A car costs about €5,000 per year between depreciation, tax, insurance, maintenance and fuel, so it's saved about €25,000 - €750 = €24,250.00 in the last five years. Cycling is insanely good for saving money and once you get used to it, it's a lot of fun too. This is probably the best thing you can do if you want to reduce your costs, just get rid of a car in favour of cycling. Yes, it will be hard at the start and yes, you will get rained on. However, it's not so bad when you know you saved €5,000 / 250 (workdays a year) = €20.00 tax free for cycling that day.
    • Insulated our attic in 2015:
      • Cost: €598
      • Savings: €204.40 per year | 2,555kWh | 587.65kg CO2 per year. So this has saved us about €204.40 * 5 = €1,022.00 so far, so we're €1,022 - €598 = €424.00 in profit. Attic insulation will sit there forever and so will comfortably live there for 25 years, giving €4,512 of savings on the initial €598.
    • Switched to an electric car in 2014:
      • Cost: €16,000 (this was back in 2014 - second hand Nissan Leafs are way cheaper now, you can replace a second petrol/diesel car if you have one, with an older Leaf now for €8,000)
      • Savings: €2,954.8 per year | 11,224 kWh per year| 1630 kgCO2 per year. €2,954.8 * 6 = €17,728.8 of savings so far. So €1,728.8 of "profit" against our old petrol car. Wahoo - this is the first time I've realised our Leaf has "Broken even" versus our old Nissan Almera. This is a bit of a hallow celebration as cars, even electric, are very expensive to own.. Better to cycle. But if you must drive, definitely switch over to an electric car.
    • We installed a wood burning stove with a back boiler in 2016 - though at this point, I recommend just going straight to a heat pump and leap frogging a wood burning stove. It was fun and we learned a lot but people on this thread rightly pointed out that it's not good for local air quality - it also turns out even efficient sealed stoves leave particulate matter inside the house - so it was fun while it lasted but I'm glad we've switched over to a Heat Pump now for all of our heating. Unless you have free wood, an electric heat pump will be cheaper to run.
      • Cost: €4000 
      • Savings: About €3000
      • Verdict: Don't install a wood stove now, just go straight to a Heat Pump to hear your house
    • Installed Double Glazed Windows and sealed front door in 2016:
      • Cost: €7,000
      • Savings: €303.21 per year | 3,790.08 kWh per year | 706 kgCO2 per year. So they've saved €303.21 * 4 = €1,212.84 so far, so we're "down" €7,000 - €1,212.84 = €5,787.16 on the windows. Though insulating your house and particularly installing new windows brings a lot of comfort and security benefits. They'll pay for themselves in 23 years.
      • Fun Fact, here's the old and new doors beside each other at the time we installed them:
      • 537071.png
    • Installed 2.2kW SolarPV Array in 2017
      • Cost: €4313 (This would cost €2513.00 today as the SEAI grant now gives €1,800 of a grant for a system of this size now)
      • Savings: €351.25 per year | 2088 kWh per year | 1,123kg of CO2 per year. So this has saved us €351.25 * 3 = €1,053.75 so far and will save €351.25 * 20 = €7,025.00 over it's warrantied lifetime
    • Insulated the House (External Insulation on the back and side wall, internal insulation on the front), Installed a Heat Pump in 2020:
      • Cost:
        • Heat Pump cost €8,500 (€12,000 - €3,500 SEAI grant)
        • Insulation (External + Internal): €9,300 (€13,800 - €4,500 SEAI grant)
      • Savings: See post above! Because this is such a big change, and is tied in with everything we've done above in terms of installing double glazed windows, switching to an EV, etc. the best way I can see to calculate savings is to look at what we used to spend on energy all up, which was €4,703.56 per year, and now we're down to €778.13 a year. This includes the changes above, but adds up to a total energy cost reduction of €3,925.43 a year.
    • Increased the SolarPV installation from 2.2kW to 5.9kW in 2020
      • Cost: €5,198.00 (€7,148.00 - €1,950 SEAI grant)
      • Savings: 4,260 kWh per year | €561.60 per year | 1,491 kgCO2 per year, so this will pay for itself in 9.2557 years and is warrantied for 20 years, so make us 561.6 * 20 = €11,232 in total on our €5,198 investment (preventing 1,491kgCO2 * 20 = 29,820 kgCO2 in the process)
      • Comment: As we had switched to an electric car, switched to heating our house an electric heat pump - everything in our house was now powered by electricity so it made sense to try to generate as much of this electricity ourselves by installing additional Solar panels on all of the remaining roof space we have. So these panels now will just sit there eating into our electricity bills for the next 20 years

    So adding all of these up: we've spent a total of €50 + €100 + €750 + €598 + €16,000 + €4000  + €7,000 + €4313 + €8,500 + €9,300 + €5,198.00 = €55,809 over the last 7 years, and it's saved us a rough estimate of €1,000 + €1,500 + €523.74 + €24,250 + €1,022 + €17,728.8 + €3000 + €1,212.84 + €351.25 + €561.60 = €51,150.23 of savings so far. Most of these investments will continue generating savings into the future - the SolarPV system is warrantied for another 19 years and will save about €10,000 over that time, the electric car is still running so will continuing "saving" versus our old petrol costs, my electric bike is still going strong with a few hours maintenance a year, the insulation is warrantied for another 24 years.. I'm guessing the €55,809 will save about €100,000 over the next 20 years. The point is that once we’ve made these investments, we reap the benefits in terms of money, increased comfort and financial security for a long time to come. It's also worth noting that we didn't magically have €55,000 on day one - we started with small things and just saved relentlessly for the next thing, which allowed us to save more money each month and so on. It made it a lot of fun.


  • Registered Users, Registered Users 2 Posts: 18,779 ✭✭✭✭kippy


    New windows, external doors and insulation are probably the biggest bang for buck in older houses from what I am seeing, with oil at its current cost. Upgrading the oil burner, depending on age makes a big difference too.
    We moved into a 2002 detached house a few years ago and haven't felt the need to invest in any of these improvements yet.
    Pretty much every other change is pretty expensive and comes with some big enough potential downsides.
    All of this of course in a world where oil remains reasonably inexpensive.
    The charging infrastructure for electric cars is still woefully inadequate but is improving. Once this happens, will probably go down this route.


  • Registered Users, Registered Users 2 Posts: 177 ✭✭ercork


    Conor20 wrote: »
    Thanks! I spent a day thinking about this to try find the right measurement to directly compare gas and a heat pump from a cost perspective. Because the efficiencies are so different, the input costs don't really make sense to compare. When heating your house, the thing that actually matters is the cost of delivered heat, so I think the right measure for us to compare is € / kWh of delivered heat. If you can get gas for €0.05/kWh with a gas boiler with an efficiency of 80%, then your cost of delivered heat is €0.05 * (1/0.8) = €0.06 / kWh of delivered heat. If Oil costs about €0.07/kWh, then it will similarly cost about €0.08 / kWh of delivered heat.

    We next need to work out our average cost of electricity for the Heat Pump. So a quick delve into the cost of electricity from the SolarPV array. It generates 4,260 kWh per year, warrantied for 20 years, 4,260 kWh * 20 = 85,200kWh over it's warrantied lifetime, €5,198 / 85,200kWh = €0.06 / kWh. I would say we're powering the Heat Pump with a mix of SolarPV, Night Rate electricity and day time electricity roughly equally, so the average electricity cost for the Heat Pump is - ( (€0.06 * .33) + (€0.08 * .33) +(€0.19 * .33) ) = €0.11 / kWh on average.

    For a heat pump with an efficiency of 440% (e.g. a CoP of 4.4 meaning for every 1kWh of electricity it consumed, it pumps 4.4kWh of heat into your house), at an electricity cost of €0.11 / kWh means €0.11 * (1/4.4) = €0.03 / kWh of delivered heat.

    So a heat pump is roughly half the cost to run, at €0.03 / kWh of delivered heat, to gas at €0.06/kWh of delivered heat or to oil at €0.08 / kWh of delivered heat.

    Good post Conor. The SEAI have also worked out these delivered energy costs for the different efficiencies/COPs. See p2 of this doc:

    https://www.seai.ie/publications/Domestic-Fuel-Cost-Comparison.pdf


  • Registered Users, Registered Users 2 Posts: 9,814 ✭✭✭antoinolachtnai


    ercork wrote: »
    Good post Conor. The SEAI have also worked out these delivered energy costs for the different efficiencies/COPs. See p2 of this doc:

    https://www.seai.ie/publications/Domestic-Fuel-Cost-Comparison.pdf

    The heat pumps section there is incorrect as far as I can tell and is best disregarded. There is no differential pricing like this for incremental consumption of electricity.


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  • Registered Users, Registered Users 2 Posts: 177 ✭✭ercork


    The heat pumps section there is incorrect as far as I can tell and is best disregarded. There is no differential pricing like this for incremental consumption of electricity.

    I think most resedential customers would be in band DD - the others can be ignored.


  • Registered Users, Registered Users 2 Posts: 9,814 ✭✭✭antoinolachtnai


    The heat pumps section there is incorrect as far as I can tell and is best disregarded. There is no differential pricing like this for incremental consumption of electricity.

    Not really. The cost for band DD includes the cost of standing charges. But the standing charges are a ‘sunk cost’. You have to pay them whether you have a heat pump or not.

    The correct cost to use for comparison is the cost per additional kWh consumed, ie the unit price the supplier quotes.


  • Registered Users, Registered Users 2 Posts: 177 ✭✭ercork


    Is 21c per unit not a standard enough price? Of course there are discounts available and one year offers and all that (think mine is 16c per unit) but in fairness to the SEAI they can't really cover all the possibilities.


  • Registered Users, Registered Users 2 Posts: 9,814 ✭✭✭antoinolachtnai


    ercork wrote: »
    Is 21c per unit not a standard enough price? Of course there are discounts available and one year offers and all that (think mine is 16c per unit) but in fairness to the SEAI they can't really cover all the possibilities.

    From a quick perusal 19.86c is the highest price in the market for an incremental unit on a 24h tariff. The SEAI price comes from an EU study that is not really relevant to pricing energy for heating.


  • Registered Users, Registered Users 2 Posts: 3,412 ✭✭✭randombar


    I'm still not sure if there is a return on heat pumps.

    Cost:
    Heat Pump cost €8,500 (€12,000 - €3,500 SEAI grant)

    Standard calculations are a 50% cost saving based on existing gas or oil.

    So I've you've a well insulated house (a requirement for HP) your oil bill could be in the region of 700/800 per year (using my own for figures). Adding a heat pump would save 400 per year. 21 years before you see a return? I know there are comfort considerations etc. but the HP cost needs to fall to 4 to 5 k or the COP needs to increase a good bit for it to be seen as a viable solution yet.

    @Conor20 just wondering how much the retrofit of UFH was per Sqm?


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    +1 GaryCocs

    I'm far from convinced "upgrading" to a heat pump system is wise, even with the huge subsidy courtesy of the tax payer and even if your house is already very well insulated

    I like the idea of it and moving away from fossil fuels to fully renewable energy is very important. But not at all costs. And certainly not it the cost projections do not hold in real life.


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  • Registered Users, Registered Users 2 Posts: 760 ✭✭✭Bif


    GaryCocs wrote: »
    I'm still not sure if there is a return on heat pumps.

    Cost:
    Heat Pump cost €8,500 (€12,000 - €3,500 SEAI grant)

    Standard calculations are a 50% cost saving based on existing gas or oil.

    So I've you've a well insulated house (a requirement for HP) your oil bill could be in the region of 700/800 per year (using my own for figures). Adding a heat pump would save 400 per year. 21 years before you see a return? I know there are comfort considerations etc. but the HP cost needs to fall to 4 to 5 k or the COP needs to increase a good bit for it to be seen as a viable solution yet.

    @Conor20 just wondering how much the retrofit of UFH was per Sqm?
    Another aspect to consider is replacement costs...how long do they last v standard boiler?


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    Another aspect is when a heat pump goes wrong, that there don't seem to be that many options to have it fixed. While any plumber can fix a gas / oil boiler. A few threads about it in the forum recently. And a gas / oil boiler rarely goes wrong, in the first 10 years of its life anyway.


  • Registered Users, Registered Users 2 Posts: 1,234 ✭✭✭vincenzolorenzo


    unkel wrote: »
    +1 GaryCocs

    I'm far from convinced "upgrading" to a heat pump system is wise, even with the huge subsidy courtesy of the tax payer and even if your house is already very well insulated

    I like the idea of it and moving away from fossil fuels to fully renewable energy is very important. But not at all costs. And certainly not it the cost projections do not hold in real life.

    I've been wondering about this too lately.

    New builds are very energy efficient and have a very low heat load. DHW is actually a bigger demand than space heating, and as this needs a higher temperature than space heating surely you're getting a low CoP? So new build owners are spending a small fortune to put in a heating system that needs to deliver a small total kWh compared to older housing stock?

    Although traditionally viewed as poor has anyone looked at storage heaters for new builds? Much lower capital cost, run at night rate electricity keeps running cost down. Not as cheap to run as HP but surely much better payback?


  • Registered Users, Registered Users 2 Posts: 65,708 ✭✭✭✭unkel
    Chauffe, Marcel, chauffe!


    Good points. We are a family of 5 with 3 teenage daughters and we use lots and lots of (really) hot water. I wonder how efficient a heat pump is in doing that. You could of course do most of it during the cheap night rate electricity, provided you have a big cylinder (ours is 360l but the standard traditional cylinder is just 120l)

    As for space heating, I am using mostly electric heaters that actually make me more money than they cost me in electricity this winter :D


  • Registered Users, Registered Users 2 Posts: 533 ✭✭✭mike_2009


    Agree about the points made about Heat Pumps. Although - Solar panels weren't "cost effective" 10 years ago, but are very nicely priced now. Efficiencies still improving too albeit slowly. Batteries will continue to get cheaper over the next 10 years and there are other forms of storage possible too (heat batteries).
    Heat Pumps aren't around as long or as popular as Gas/Oil boilers but these have peaked in terms of efficiency and price. Hybrid heat pump / gas / oil boilers are available today and over the next 10 years the number of heat pumps manufactured and installed will drive prices down and skillsets up. At least that's what should happen!
    I wonder about risks to gas/oil supplies but even our Electricity supply relies heavily on gas but in 10 years hopefully less so. If we have turbulent times ahead due to climate migration and national isolationism I wouldn't be betting heavily on an imported fuel. I'd even say electricity power cuts will become a regular occurrence given our current power sources and the lack of new capacity/retiring of old plants.
    Should each household hang onto alternate means of space heating / water heating but how far out do you go on that particular branch?
    Agree that if you're lucky enough to live in a newer house space heating is relatively easy compared to hot water. Night rate for hot water 1:1 is still affordable but look at all the taxes add to the Electricity bill, prices still rising. CO2 heat pumps are better geared to delivering higher temps but may not be suitable to the Irish Climate (higher humidity) from what I've heard. Still the idea of getting 3 or 4 times the unit of heat per kWh is attractive. Will it last 10 years though? With annual maintenance there's no reason it shouldn't last over 20 years if it's a good quality model from what I've read.
    Anyone have any hot springs near them they can tap into?
    Excellent points made by everyone here and thanks to the O.P. for his recent update - inspiring!


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