What’s the cost of a 5 minute 8.5Kw shower in 2017/2018 ?

irelandjnr

We are with Electric Ireland, if that matters.

fleet

Depends on your unit rate, which may vary depending on time of day (Nightsaver type plans etc.)

But a typical rate of 17.5c per kWh.

(5/60 minutes) * 8.5kW * 17.5c per kWh = 12.39c

irelandjnr

fleet wrote: »

Depends on your unit rate, which may vary depending on time of day (Nightsaver type plans etc.)

But a typical rate of 17.5c per kWh.

(5/60 minutes) * 8.5kW * 17.5c per kWh = 12.39c

Cheers. Just one more follow up. Would you happen to know how much water these electric pump showers (T90XR) use at full power every five mins?

oxygen

5 minutes :eek: Mine last a half hour.
I need to have words with myself...

Sleeper12

irelandjnr wrote:

Cheers. Just one more follow up. Would you happen to know how much water these electric pump showers (T90XR) use at full power every five mins?

3 litres per minute in the winter and up to 4 litres per minute in the summer when the water in the attic tank is warmer.

Electric shower are the most economical way to shower. The only thing cheaper is solar heated water

irelandjnr

oxygen wrote: »

5 minutes :eek: Mine last a half hour.
I need to have words with myself...

It wasn’t me and it may be a half hour. Was going to use 5 minute increments to calculate various shower durations ;-)

GarIT

Sleeper12 wrote: »

The only thing cheaper is solar heated water

Solar heated water is a scam. The price of the panels + maintenance makes it uneconomical. At least 6 months of the year the price of a pump outweighs the cost of heating the water to the temperature a water heater panel would get it.

If you want to be economical get real solar panels that generate electricity and use the emersion. During the heating process, it might cost more than using solar water heaters but over the course of a day the solar makes up for it and the panels are much more economical.

2011

Sleeper12 wrote: »

Electric shower are the most economical way to shower. The only thing cheaper is solar heated water

I don't agree.

Per unit gas costs about €0.05 so even if your boiler is only 85% efficient it will cost far less to heat the same volume of water to the same temperature.

2011

GarIT wrote: »

Solar heated water is a scam. The price of the panels + maintenance makes it uneconomical.

I agree that return on investment can be > 20 years for some if it is a retro fit, so as such does not make financial sense in many cases. However on a new build it is a different story.

At least 6 months of the year the price of a pump outweighs the cost of heating the water to the temperature a water heater panel would get it.

I would be interested to see a calculation to back this up.

If you want to be economical get real solar panels that generate electricity and use the emersion.

Disagree completely.
Assuming that you accept that 3kW is the minimum size for a reasonable immersion element:
Have you any idea how much roof area is required for 3 kWp of PV panels? Do you know what this would cost a lot to install, and how much water you would heat with it?

Sleeper12

2011 wrote: »

I don't agree.

Per unit gas costs about €0.05 so even if your boiler is only 85% efficient it will cost far less to heat the same volume of water to the same temperature.

You are totally correct. Gas is much cheaper than electricity. The problem is unless you have a combi boiler you can't just heat the exact amount of water. Heating the hot water cylinder for water for a shower won't be as cost effective as an electric shower as there is no wasted hot water.

Idbatterim

Sleeper12 wrote: »

3 litres per minute in the winter and up to 4 litres per minute in the summer when the water in the attic tank is warmer.

Electric shower are the most economical way to shower. The only thing cheaper is solar heated water

shower from natural gas combi boiler will be cheaper...

Oasis1974

You could really spend 30 minutes under a shower a day?

2011

Sleeper12 wrote: »

The problem is unless you have a combi boiler you can't just heat the exact amount of water.

True. If it is one very short shower possibly, but it wouldn’t be as good a shower due to lower flow rate / pressure.

I normally put my gas boiler on for 30 minuets. This provides sufficient hot water for 2 x 8 minute (approx) showers. If I were to use an instantaneous electric shower not only would the flow rate be less but it would cost more.

Heating the hot water cylinder for water for a shower won't be as cost effective as an electric shower as there is no wasted hot water.

No hot water is wasted, by the end of the second shower it is pretty cold.

Sleeper12

Idbatterim wrote:

shower from natural gas combi boiler will be cheaper...

Totally agree but again the shower from the combi boiler will be putting out more than 3 litres per minute. This would usually put them as more expensive per litre

2011

Sleeper12 wrote: »

Totally agree but again the shower from the combi boiler will be putting out more than 3 litres per minute. This would usually put them as more expensive per litre

No, cheaper to heat by gas per liter but a greater number of liters. Even if twice the volume was used it would still be cheaper with gas as the unit rate is ⅓ the cost of electricity.

2011

2011 wrote: »

Have you any idea how much roof area is required for 3 kWp of PV panels?

Somewhere around 25m²

2011 wrote: »

Do you know what this would cost a lot to install,

Varies, I don't pay more than €0.60 a watt on used panels...never had a problem with any of them. Self-install there really isn't much to them.

2011 wrote: »

and how much water you would heat with it?

Spring to Autumn between a quarter ton and a half ton +35°C a day assuming no losses and full output was directed to water heating

2011

Sir Liamalot wrote: »

Somewhere around 25m²

That is a lot of south facing roof space.

Varies, I don't pay more than €0.60 a watt on used panels...never had a problem with any of them.

So €1800 for 3kWp. Where do you buy 2nd hand solar panels?
What other kit do you use? Are you syncing with the mains?

Self-install there really isn't much to them.

Spring to Autumn between a quarter ton and a half ton +35°C a day assuming no losses and full output was directed to water heating

Why would you heat 250 to 500 litres of water a day and why heat it to such a low temperature?

This would mean a maximum of 500 x 4184 x 35 = 73.24 MJ
So an average output of 424 (Spring to Autumn) to 848 watts (Summer).
Pretty impressive.


Any pictures?

Sleeper12

2011 wrote: »

No, cheaper to heat by gas per liter but a greater number of liters. Even if twice the volume was used it would still be cheaper with gas as the unit rate is ⅓ the cost of electricity.

If I run the hot tap at my kitchen sink filling a liter jug till I get hot water I'll fill 6 jugs. This means when I'm finished I leave 6 liters of hot water in the pipe as wastage. This is called the dead leg.

If you have a combi boiler in the attic or downstairs you'll have a dead leg of at least 6 liters. An electric shower will only use 15 liters for a five minute shower at this time of year.

I'd argue that there's very little difference in the cost of a 5 minute shower between an electric shower & a combi boiler. Factoring in using more than 3 liters per minute with a combi boiler & the dead leg, a combi boiler could be more expensive to run then an electric shower for a 5 minute shower.

I've a shower backing onto the hot press & have a dead leg of over a liter even this close to the hot water cylinder. Heating your cylinder with gas is cheaper than electricity but you will heat a lot more than the 15 liters & the 1 liter dead leg. Then you won't be happy with 3 liters per minute coming from your cylinder so you put a shower pump on. You are now showering in 10 to 20 liters per minute.

When you look at everything together I still recon an electric shower is the cheapest option for a 5 minute shower. Your electric shower costs around 300 every 10 years in repair of replacements where using the gas boiler to heat the water would have no effect on the maintenance of the boiler

Electric showers are my business but even at that I say give me a power shower any day. My own shower pumps out 23 liters per minute. I can drain the tank in 10 minutes but I love it!

exaisle

30 minutes in the shower???

How to have a quick shower:

1. Wash up as far as possible.

2. Wash down as far as possible.

3. Wash possible! ;-)

2011

2011 wrote: »

That is a lot of south facing roof space.

It's roughly 1m² per 100w but they are getting more efficient every year.

2011 wrote: »

So €1800 for 3kWp. Where do you buy 2nd hand solar panels?
What other kit do you use? Are you syncing with the mains?

You're the one said 3kW, 2kW is adequate with energy conservation.
Ebay Uk because the uptake on them is much higher and there's a bigger market. Re is 5 years behind Europe in it's perceptions of it's utility.

Well I mostly DC couple because grid tied and alternating current is of little interest to me.
MorningStar charge controllers, Kraus and Naimer cam switches and Albright contactors are my only hard-won loyalties.
The rest of my personal systems are made of whatever was vaguely suitable that I could get for cheap. I buy a lot of broken kit and fix it.

I've 550W syncing with mains on a cheapo 600W GTI I wouldn't recommend.
No brainer really: Panel -> DC Isolator -> DC Powermeter -> GTI -> 3A RCBO -> AC Isolator -> AC kWh Counter & Power Meter -> Distribution Board.

2011 wrote: »

Why would you heat 250 to 500 litres of water a day and why heat it
to such a low temperature?

I wouldn't but one could if one wanted with 3kW of solar available
Assuming the air temp. is 15°C + 35°C = 50°C ...how hot do you want yer shower?

2011 wrote: »

This would mean a maximum of 500 x 4184 x 35 = 73.24 MJ
So an average output of 424 (Spring to Autumn) to 848 watts (Summer).
Pretty impressive.

I could give you the long calculation on solar azimuth, temperature derating, inverter efficiency, panel aspect, panel efficiency etc...
or you can take my word for it per 100Wp of PV you hang you'll get between 300Wh to 650Wh per day March to October.
Hence I design systems to 3X rated power in daily energy.

2011 wrote: »

Any pictures?

Photos? Old ones. Builder's house and all that. I'm souping up the motor and working on a friend's boat atm.



12kWh battery @ 48V
1.5kWh battery @ 12V
2.4kVA Marine Inverter Charger does the job, not worth the RRP
6kVA Low Frequency AC Coupling Inverter Charger, currently not operational.
45A MPPT charge controller derated to 37.5 due to amputated FET
45A PWM Charge controller
30A 12V PWM Charge Controller
400A Motorised 3P DC Switch-Disconnect




100A of Solar Charge Control, DC Isolators and ChangeOvers (battery / grid tie)




48VDC Distro. 350A Capable. Fused at 80A.

2011

Sir Liamalot wrote: »

You're the one said 3kW, 2kW is adequate with energy conservation.

Actually I said "Assuming that you accept that 3kW is the minimum size for a reasonable immersion element". I picked this value as it is generally accepted to be the most standard domestic immersion element size.

Ebay Uk because the uptake on them is much higher and there's a bigger market. Re is 5 years behind Europe in is perceptions of it's utility.

I would not say that many people will remove PV panels that are performing well. I accept that there is the odd exception that can be picked up by those that know what they are looking for (like you). I think that you will accept that in reality there are not many people that can do this.

Well I mostly DC couple because grid tied and alternating current is of little interest to me.
MorningStar charge controllers, Kraus and Naimer cam switches and Albright contactors are my only hard-won loyalties.
The rest of my personal systems are made of whatever was vaguely suitable that I could get for cheap. I buy a lot of broken kit and fix it.

I can see why this works for you. Clearly you know what you are doing and are quite passionate about this. Most people do not have this expertise or time and interest to gain this expertise.

Assuming the air temp. is 15°C + 35°C = 50°C ...how hot do you want yer shower?

I'm assuming that the cold water tap temperature is about 7°C. So if I heat it by 35°C (as you suggested) then it will reach a temperature of 42°C which for a shower a bit cold, especially when you consider that there will be a further heat loss before it reaches the shower.

I could give you the long calculation on solar azimuth, temperature derating, inverter efficiency, panel aspect, panel efficiency etc...
or you can take my word for it per 100Wp of PV you hang you'll get between 300W to 650W per day March to October.

A watt is a joule per second. So when you say "300 to 650W" you need to tell me how long this is for so that I can work out the energy output.

I don't know if this is 300 to 650W for a second, an hour or ten hours per day? Can you tell me how many joules per day, how many kWh per day or how many watts per hour on average? Is my earlier calculation an accurate reflection ?

My earlier calculation:
Max energy output per day 73.24 MJ
Average output of 424 (Spring to Autumn) to 848 watts (Summer).

The photos look very impressive, clearly you know what you are doing. I take it that your installation costs for labour are zero as you install them yourself and you pay less for materials as they are second hand.

My response was to GarIT who I suspect (but I am open to correction) like the vast majority of people does not have your expertise, enthusiasm or experience.

The average person with little or no technical understanding of installing PV panels to heat water will have a far longer pay back period. This is especially the case when you consider that for the vast majority of people the panels will be new and they will have to pay a specialist to install them. Add into this the fact that many of those that claim to be specialists are not that special (some may even call them chancers)

The company I am working for (we specialise in energy optimisation projects) plans to install industrial scale PV arrays in the near future, so this is an area I am interested in.

2011

2011 wrote: »

Actually I said "Assuming that you accept that 3kW is the minimum size for a reasonable immersion element". I picked this value as it is generally accepted to be the most standard domestic immersion element size.

2011 wrote: »

Have you any idea how much roof area is required for 3 kWp of PV panels?

I think you are working under the assumption that the solar array has to work in direct drive. This is not necessary you just need to insulate the water tank.

2011 wrote: »

I would not say that many people will remove PV panels that are performing well. I accept that there is the odd exception that can be picked up by those that know what they are looking for (like you).

I bought 500Wp that regularly produces 550Wp. I've a 265W was a reject because it wasn't as black as the rest (which I verified myself to be true), I've 2 x 240W that were used to test a racking system load bearing capability, that were looking for a home after testing was complete. Also have 1kWp of cracked amorphous modules (free) that are mostly working fine but just need some UV glue injected. I'm decommissioning a 150Wp module myself that has on occasion produced 120% rated because I'm upgrading to a 265Wp and there's no room for the old, which I may or may not sell depending on whether I can find a use for it.

2011 wrote: »

I think that you will accept that in reality there are not many people that can do this.

Point at sun, meter under load...hrmm sadly I agree.

2011 wrote: »

I can see why this works for you. Clearly you know what you are doing and are quite passionate about this. Most people do not have this expertise or time and interest to gain this expertise.

I wasn't recommending a DC coupled system which is what I'm building x3.

AC coupling is lossy and easy peasy. I installed mine in 1.5 days and most of that was mechanical.

2011 wrote: »

I'm assuming that the cold water tap temperature is about 7°C. So if I heat it by 35°C (as you suggested) then it will reach a temperature of 42°C which for a shower a bit cold, especially when you consider that there will be a further heat loss before it reaches the shower.

It takes the same energy to heat 1 litre of water 1°C. If you want hotter, then heat less volume. Most water tanks are substantially smaller than a quarter ton. It was just an example calc.

2011 wrote: »

A watt is a joule per second. So when you say "300 to 650W" you need to tell me how long this is for so that I can work out the energy output.

Consider the water tank a heat battery, in which case time is only relevant to offset installation heat loss.

300Wh to 600Wh per day, sorry for confusion, will correct above.

If you want specific figures try this

2011 wrote: »

The photos look very impressive, clearly you know what you are doing. I take it that your installation costs for labour are zero as you install them yourself and you pay less for materials as they are second hand.

Yurp and I'm not afraid to buy broken gear. I was expecting you to tell me the PE is too small...cos it is. There's another 10mm² PE conductor on the DC distro grounding plate outtov sight but I have to upgrade it to one size smaller than the biggest DC conductor. Which if I can resurrect the 6kVA, 18kVA surge then it'll be about 50mm² (thin wall ELVDC Cable rating not low voltage)

It's not a commissioned system although I can get it up and running in a power cut.

2011 wrote: »

My response was to GarIT who I suspect (but I am open to correction) like the vast majority of people does not have your expertise, enthusiasm or experience.

You asked for photos, that's what I got, it's a highly efficient system. You can simplify it by a factor of 5 if you didn't care about system losses and want to believe what the inverter/charger/charge controller manufacturers tell you.

As I say AC coupled batteryless grid tie is a no-brainer. You can buy plug and play inverters on the mainland but they're not legal here. (Very little is....brown envelope sh**e as usual)

2011 wrote: »

The average person with little or no technical understanding of installing PV panels to heat water will have a far longer pay back period. This is especially the case when you consider that for the vast majority of people the panels will be new and they will have to pay a specialist to install them.

Add into this the fact that many of those that claim to be specialists are not that special (some may even call them chancers)

Indeed...I fix a lot of systems "specialists" install.
I wouldn't let them turn a screw near my systems...there's a mentality of acceptable embedded losses which while it is the only economically viable way to operate commercially aggravates me no end.

2011 wrote: »

The company I am working for (we specialise in energy optimisation projects) plans to install industrial scale PV arrays in the near future, so this is an area I am interested in.

First agenda please build a grid tie inverter that only powers up when it is a generator. This time of year they're all running as parasitic loads in low light across 52°N.

When you do, let me know because I'll be interested.

Second agenda. Please make a batteryless DC MPPT proportional controller for water heating. Why does everyone have to use an inverter with associated losses to power a resistive element?

When you do, let me know because I'll be interested.

Third agenda. Please, please, put them on the bloomin' rooves and stop doing cheapo ground mounts competing with agriculture! :mad:

flaneur

A few points:

Water usage - electric showers don't heat instantly and you will be standing there waiting for the elements to come to fill temp before you shower. This is at least bad as any piping lag to a highly insulated tank.

You also can't pause electric showers as they rely on steady flow. If you stop the flow the temperature goes way up. That's again introducing more water waste if you want to shampoo etc.

kWh use and cost of kWh vs high efficiency boiler + highly insulated tank + solar. I'm seeing a lot of statement of speculation as fact here.

My solar water system can produce at least a good % of the hot water temperature raise during the winter and in summer it's producing more heat than I can get rid of!

I've a large, very well positioned, south facing roof mounted collector and they thing can really heat! I've been shocked at how much energy it picks up! You could boil tank on a summer's day!

Also I've a two circuit boiler, so the heat exchange loop into the tank can be run at the optimal temp to get the boiler to maximum condensing efficiency.

The tank is EXTREMELY well insulated and the hot water pipework is extensively lagged.

I also find the thermostatic control on a good shower mixer vastly superior to an electric shower. All they do is control the flow rate through the element. You can't even set a temperature. The flow rate on my system also has no relationship not the temperature. Whereas on an electric shower, flow is directly and inversely proportional to temperature.

Slight water pressure changes also result in unstable temp in electric showers.

There are a lot of variables in stored systems, considering many Irish houses still have a totally insulated cooper cylinder often with nothing more than a badly fitted lagging (or even none at all). You've also got huge variation in quality and age of lagging or even nonexistent lagging.

So one gas and solar modern system with very high level of insulation could be very efficient, while some older houses have really very primitive setups that are woefully inefficient at heating domestic hot water.

The most expensive method possible is a badly insulated, old copper tank and electric immersion. You're basically just heating the hot press cupboard.

Maggie Marie

Sleeper is spot on the money here with the electric shower. Not sure of what the other posters are arguing about.

flaneur

Sleeper12 wrote: »

Totally agree but again the shower from the combi boiler will be putting out more than 3 litres per minute. This would usually put them as more expensive per litre

It depends how you adjust the shower mixer and flow rate. There isn’t just one type of shower. You could have a very miserly efficient low flow system or a very high flow pumped system lashing water out at huge rates.

ted1

fleet wrote: »

Depends on your unit rate, which may vary depending on time of day (Nightsaver type plans etc.)

But a typical rate of 17.5c per kWh.

(5/60 minutes) * 8.5kW * 17.5c per kWh = 12.39c

That's providing its up full, I know we have the temperature set for about 60% so slow for the pump say it's down to 8c for 5 minutes

2011

ted1 wrote: »

That's providing its up full, I know we have the temperature set for about 60% so slow for the pump say it's down to 8c for 5 minutes

The load is almost entirely due to the heating element. This will consume the same power regardless even if the heat setting is turned down to 60%, it will simply allow more water to pass over the element within a given time.

dathi

ted1 wrote: »

That's providing its up full, I know we have the temperature set for about 60% so slow for the pump say it's down to 8c for 5 minutes

its the flow rate of water through the shower that regulates the temperature of water, the power to the element remains the same

myshirt

Is this in any way tied to the thread over in the Accommodation forum where tenants are seeking to carry out precise calculations on their share of the electricity bill so they don't get shafted?

2011

myshirt wrote: »

Is this in any way tied to the thread over in the Accommodation forum where tenants are seeking to carry out precise calculations on their share of the electricity bill so they don't get shafted?

Just paste link to this thread in a post on the other forum.

Sleeper12

myshirt wrote: »

Is this in any way tied to the thread over in the Accommodation forum where tenants are seeking to carry out precise calculations on their share of the electricity bill so they don't get shafted?

There is an ESB appliance calculator app you can get. Pretty handy to give you a rough idea of where your money is being spent

Vronsky

Sir Liamalot wrote: »

It's roughly 1m² per 100w but they are getting more efficient every year.




You're the one said 3kW, 2kW is adequate with energy conservation.
Ebay Uk because the uptake on them is much higher and there's a bigger market. Re is 5 years behind Europe in it's perceptions of it's utility.

Well I mostly DC couple because grid tied and alternating current is of little interest to me.
MorningStar charge controllers, Kraus and Naimer cam switches and Albright contactors are my only hard-won loyalties.
The rest of my personal systems are made of whatever was vaguely suitable that I could get for cheap. I buy a lot of broken kit and fix it.

I've 550W syncing with mains on a cheapo 600W GTI I wouldn't recommend.
No brainer really: Panel -> DC Isolator -> DC Powermeter -> GTI -> 3A RCBO -> AC Isolator -> AC kWh Counter & Power Meter -> Distribution Board.





I wouldn't but one could if one wanted with 3kW of solar available
Assuming the air temp. is 15°C + 35°C = 50°C ...how hot do you want yer shower?

.

Is it not dangerous to have warm and not hope water constantly in the boiler?
I was always told that the boiler had to be set to 60C to kill off legionnaires.

myshirt

Sleeper12 wrote: »

There is an ESB appliance calculator app you can get. Pretty handy to give you a rough idea of where your money is being spent

What's next? Drilling a hole in the fridge to make sure the light definitely does go off and that you are not being unnecessarily charged?

Sleeper12

myshirt wrote:

What's next? Drilling a hole in the fridge to make sure the light definitely does go off and that you are not being unnecessarily charged?

That's silly. I use a camera for this.

I press the door switch.