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Independence of the grid

  • 11-04-2023 4:35pm
    Registered Users Posts: 116 ✭✭

    My ultimate goal is to upgrade my electrical installation to achieve the independence of the grid.

    I know this is not entirely possible and you always need to be, at least, connected but that's the aim.

    Based on what I read so far my idea is to put Solar PV, a power diverter for the hot water, and a heat pump.

    There is a lot of "Read this" and "read that" but in fairness, the information is overwhelming. It is not a lack of information, it is just hard to process it. So in order to keep me focused and on the right track. What are the main points you think I would need to have into consideration to achieve the maximum degree of independence of the grid?

    I have an oil boiler at the moment. Do you think, it would save electricity to change to a heat pump? The house is not greatly insolated just yet.

    Is it worth the power diverter? We have an electric shower and we don't use the immersion (although it would be nice to have hot water in the tap)

    is it worth solar panels for a 20-year-old house?

    Regarding any of this, any specific providers that ye would recommend?


  • Registered Users Posts: 230 ✭✭johnbk

    One important question before proceeding is how many kWh are you using annually on average over the last three years. Any meaningful answers here would need this information. Check bills and put the answer here.

    My recent step into the world of solar pv has been beyond my expectations. However I don’t ever envisage independence from the grid in the three winter months but the rest of the year is a possibility.

    My views are my own.

  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    Independence of the grid? Right into the deep end 😂. For that you need a lot of solar, lots of batteries, and possibly a bit of wind and a generator. And a lot of cash.

    Let's put a pin on that for now.

    is it worth solar panels for a 20-year-old house? Yes, as long as you don't overpay for it.

    The hot water diverter just runs your immersion.

  • Registered Users Posts: 5,112 ✭✭✭John mac

    The house is not greatly insulated just yet.

    first thing is insulation .

    heat pump is no good if the insulation isn't there to keep the heat in .

  • Registered Users Posts: 116 ✭✭UnhappyCustomer

    Edited. Next comment

  • Registered Users Posts: 116 ✭✭UnhappyCustomer

    Hard to know, I’ve bought this house 6 months ago

    what do you mean I don’t overpay for it? I suppose everything in life is worth until you don’t overpay for it 😂😂

    Working on it. The idea of getting the heat pump was to reduce the electricity bill.

    Not sure if that would actually reduce it

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  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    I mean shop around, there is some outrageous quotes out there.

    Although a heat pump will increase electric costs... But you won't be buying oil.

  • Registered Users Posts: 1,421 ✭✭✭Big Lar

    I also have a 20Yr old house and am quite confident that a heat pump just will not heat the house, unless I spend massive monies on super insulating the house.

  • Registered Users Posts: 2,463 ✭✭✭bullit_dodger

    You might be in the same position as myself (and possibly Graeme?) I'm thinking of a high temperature heat pump. Some of them can knock out 65-70C which would mean that we can use our existing radiators and treat it as if it's a more traditional boiler.

    The COP isn't as high as a normal HP (which is about 3-4), the high temp ones are more like 2x - but it's something to consider anyway. With Gas prices rising and electricity probably going to go back down to more "normal" levels, it might become ecomonically viable. That said, I'll probably run my gas boiler until it needs replacing. It owes me nothing, but if I'm forced to replace it....

  • Registered Users Posts: 1,421 ✭✭✭Big Lar

    Normally €1000-€1500 of oil covers the house heating every year, the heat pump would probably pay back over the years but then that leads to the next issue when in the cold dark months solar is scarce, most likely have to rewire the house or get in an enhanced supply to power EV, Battery Charge and Heat Pump together or choose one over the other 😮

  • Registered Users Posts: 2,463 ✭✭✭bullit_dodger

    I've thought the same problem Big Lar. Still a standard 63A domestic will give you 14.5Kw. Unkel probably hits that or close to that every night with the submarine batteries that he's got going. Give 5Kw say from 1am to 7am to an EV still leaves you with 9Kw to play with, it's doable. Though the oven and a Triton T90 (9kw) switched on with the EV would break that 14.5Kw limit.

    Wonder if they'll start to roll out 2 hot phases like they do in the US.

    Guess this is going in DIRECT opposition to the original post about grid independence though :-) ...... and my thoughts on that is that grid independence will never realistically happen with solar, but you can effectively get very close for 8-9 months of the year with panels and a battery.

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  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    A heatpump can heat a drafty barn with a decent COP if it has

    >Enough output to match demand

    >Enough emitters (radiators) to output the heat.

    My house is 40 yrs old, and running experiments with the tank I have, I can heat the house with 40-50c water.

    Although most of my radiators aren't the original ones, they are nearly all double radiators. Really helps when the stove is trying to heat the house.

    I do think I need to remove them all and flush them out though. Esp the one in the living room.

    The Ecoforest has been recommended by a plumber friend, for instance the ecoAir 3-12 has a cop of 3 with the Air at 7 W at 55, That would be it leaving the heatpump at 55. Looks like it can vary the output of the heatpump too.

    Scrolling on down, the max power requirement is 3.5kw So for every 3.5kwh of electric it will be pushing 10kwh of heat.

    If Ive been away all day, I have run one or both immersions in my tank to warm up the house before i got home, 3kw can almost keep it at bay if its not too cold out, but 6 it does get ahead. If I went heat pump I wouldn't be looking for a grant, it would just be a drop in heat source for my tank. Id love to get 9kwh of heat for 3kwh of electric!

    Hah, we'll never have 2 hot phases, that only gets them 240, Although I could see more 3 phase going in. For older houses 12KVA should be fine, EV charge point can load balance, the rest should be fine. I am on a 16kva supply though.

  • Registered Users Posts: 4,911 ✭✭✭paulbok

    I wonder will we see ESB Networks embarking on a major line upgrade around the country, like the NBI fibre scheme in the near future?

    With the push to get everyone onto EVs and hear pumps, and assuming the country can triple its current generation to meet that demand, there will be many houses/lines that won't have the capacity to provide enough power on demand.

    I'm on a dead end line that was supposed to be upgraded two years ago as the couple of current houses/ farms on it requires far more power than it is able for, according to the Networks chap I spoke to at the time, and suffer from the occasional brown out. They were to upgrade the local transformer so the line would be able for multiple EVs charging etc, in the future.

  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    This was before my time, but my Dad says we were the same, getting brown outs etc had esb out and everything "was fine"

    Just so happened that our barley crusher and the neighbours was put on at the same time one day... Put it this way it was not fine, and the transformer had to be changed, 😜

    We only recently changed that crusher and it only pulled 3-4kw,

    Although I don't think that will work now 😂

  • Registered Users Posts: 4,911 ✭✭✭paulbok

    When a lot of rural lines were installed in the 50's, each house would have a had a few lights, couple of sockets with perhaps a kettle, radio, fridge and maybe a cooker connected, the supply required would be minimal compared to now with very few having any more work done on the line apart from maintenance. Add in EVs Heat Pumps and some farm equipment usage on top and they are bound to struggle

  • Registered Users Posts: 116 ✭✭UnhappyCustomer

    It is not even that it won't heat the house, I think it will make the Solar panel insufficient or the consumption will be huge on top of overloading the heat pump.

    I don't fully understand this, so your point would be to increase the temperature of the heat pump to, for example, 40 degrees to get 20 degrees in the house? How would that affect the heat pump consumption wise? and are these kind of HP considerably more expensive or more or less the same?

    I wonder what would be more costly. Fairly insulated house + oil boiler (oil + electricity) or poor insulated house + heat pump.

  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    More insulated house will always be cheaper no matter the heat source.

    The need for high temperature heat pumps, is to work more like the oil boiler, and the existing radiators.

    Im picking numbers out of the air here but for instance a room needs 1000w to heat a room.

    and at 60c (water temperature) the radiator in the room puts out 1000w.

    But say at 35c the same radiator only outputs 500w.

    to heat the room at 35c (where normal heat pumps are way more efficient) you would need double the radiators in the room, OR reduce the amount of heat the rooms need (insulate) That heatpump should get between 4-500% efficiency (1kwh of electric will get 4-5 kwh of heat)

    A high temp heat pump might only get 300% efficiency (1kwh electric, 3kwh heat)

    1 litre of oil has 10kwh of heat, but with boiler inefficiencies, its more like 8kwh, depending if its a condensing, and age of the boiler.

  • Registered Users Posts: 2,463 ✭✭✭bullit_dodger

    Just to expand a little on what Graeme mentions above. Boilers (gas/oil) usually heat water to 70-75c for the heating. Obviously that works well in heating the rooms.

    Heat pumps, when you get those COP's (Coefficient of performance) of 3-4 or sometimes more, usually heat the water in the pipes to 55C or so. To go higher like 65C-70C you can do that with a heat pump, but you typically reduce the performance from 3-4x to closer to 2x. Now your still getting benefit from the heat pump, but it's not as good.

    So why not just use 55C then? You can , but at lower temperatures you often have to replace the radiators that you have with bigger ones. Swapping single radiators to double ones and/or larger ones. This requires thicker pipes to carry more warm water than the 1cm/half inch pipes that are typically installed for old radiators, so you have to dig through walls/floors replacing pipework additionally. All this is doable of course, but if you can just use higher temp water, you avoid that cost.

  • Registered Users Posts: 49 Sligobuck

    @bullit_dodger This requires thicker pipes to carry more warm water than the 1cm/half inch pipes that are typically installed for old radiators, so you have to dig through walls/floors replacing pipework additionally. All this is doable of course, but if you can just use higher temp water, you avoid that cost.

    Avoid that route and put the cost into aluminum rads which require much less water than the existing rads and put out double the heat.

  • Registered Users Posts: 2,463 ✭✭✭bullit_dodger

    While that's true, it's primarily a question of "flow rate" and amount of energy that the hot water you have going through the pipes. If you have higher temperature water you can get away with a lower flow rate around your house. Graeme above explained it pretty well.

    Replacing with aluminuum rads would help, but the whole issue about using a higher temp heat pump is to avoid the work in replacing pipework and or radiators. I've 9 radiators in my semi-detacted house in D16. Replacing those would be expensive.....and I'd still have the issue about lack of flow rate.

    It's a part of the wider problem about heat pumps and them getting a bad rep about performing poorly. Often it's not the heat pump which is at fault, but the wrong application of heat pump to the house in question.

  • Moderators, Home & Garden Moderators Posts: 5,889 Mod ✭✭✭✭graememk

    Generally half inch at the radiator is plenty, it's what's under the floor that feeds it could be an issue. I know mine is 3/4 in the screed bar the last radiator or 2,

    Microbore pipe has issues though it's hard to get enough flow on them.

    But I agree you don't want to be digging your floors up!

    Gonna have to bite the bullet sometime and get on with it 😆

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  • Registered Users Posts: 116 ✭✭UnhappyCustomer

    Thanks both for the explanation. Crystal clear now. What I’m wondering if it wouldn’t be cheaper to improve the insulation of the house and put the oil boiler in the evenings rather than having a heat pump running 24/7.

    €1000/1500 in oil + the electricity I supposed covered by the solar panels.

    if it is not covered, at least it pays off during the summer when you sell electricity back to the grid.

    it sounds like heat pump is just good under perfect conditions and in this case our old houses are far from those.

    also the good auld stove could help to warm up the place.

    I supposed depending on your expectations regarding temperature. I don’t need to be in T-shirt and underwear all year around inside my house.

    also, if you have to change the floor anyways, what do you think of the underground heating?