Can I power an electric shower from my solar batteries?

[JohnD]

.

 

[JohnD]

Family of four, showering 3 times a week is £6 a week at 50p. That said I think we take longer than 10 minutes to be honest, more like 20.
We have full batteries for over half the year, 26 weeks, makes that a potential cost saving of £156.
In reality it would be almost double that, so more like £250 to £312 a year.
That’s not a bad saving ?

How many kWh per day do you get from solar in summer? And how many kWh do your batteries store?

IME it is negligible for about 6 months of the year

My gas bill for HW is less than 50p a day, though I am still on a 2-year price fix.

How big is your hot-water cylinder?

 

[petercoupe]

if you water is heated by gas its 1/3 the cost for the same energy input
i think your battery output will be far better aimed at electrical use
you must also consider perhaps 20-30% percent off assumed stored energy or possible energy input as not actually being there as inefficiency being well below your expected levels it could be far less a failing battery will show its 100% charge but if its old it may be as low as say 20% capacity so dont assume 100% means maximum when it can infact mean perhaps 15-25% capacity

in fact old phone batteries would reach 100% charge in 10 - 15% off required time so no real capacity

Problem is I can’t really see how I can use more electricity in the summer.
I’m using it for DHW, cooking, dishwasher, laundry, air con, charging the car - but I’ve still got plenty left!
which is why I asked the original question.
I’m basically a tight bastard.

 

[petercoupe]

How many kWh per day do you get from solar in summer? And how many kWh do your batteries store?

IME it is negligible for about 6 months of the year

My gas bill for HW is less than 50p a day, though I am still on a 2-year price fix.

How big is your hot-water cylinder?

Yesterday we had 8 kw into the battery, and exported 14 kw. So, 22 kw total.
It will get better as we move into Summer.
We have a combi boiler but no cylinder. I had considered installing some form of immersion heater / cylinder too, but installing an electric shower seemed easier.

 

[robinbanks]

Problem is I can’t really see how I can use more electricity in the summer.

Sell it to the neighbours!? If you cannot export it to some anonymous electrical neighbour via the grid, perhaps your immediate neighbours could buy batteries, hot water tanks etc that your excess power will charge up

 

[SpecialK]

You can install an un-vented tank and have a solar diversion valve to bypass the combi if the tank is hot.

 

[petercoupe]

You can install an un-vented tank and have a solar diversion valve to bypass the combi if the tank is hot.

That sounds ideal.

Where can I get details?

 

[flameport]

installing an electric shower seemed easier.

It's easier, but an electric shower will be a trickling disappointment after using a shower from a combination boiler.

 

[Why Not Indeed]

I would point you to another recent thread about PV diverters but it's full of irrelevant b*llocks about how to represent formulas.
Heating a water cylinder with excess solar rather than powering an electric shower off a battery charged with excess solar means you can use the hot water for things other than showers.
Heat leakage from the cylinder will warm your living space slightly, this could be a good or a bad thing.
How are you going to decide how much to divert to charging battery and how much to divert to heating water?

 

[petercoupe]

I would point you to another recent thread about PV diverters but it's full of irrelevant b*llocks about how to represent formulas.
Heating a water cylinder with excess solar rather than powering an electric shower off a battery charged with excess solar means you can use the hot water for things other than showers.
Heat leakage from the cylinder will warm your living space slightly, this could be a good or a bad thing.
How are you going to decide how much to divert to charging battery and how much to divert to heating water?

I was hoping to warm the water first, then switch to battery charging once the water had reached a pre determined temperature. That said, I will be doing a lot of reading from here on in to work these things out.

 

[big-all]

Problem is I can’t really see how I can use more electricity in the summer.
I’m using it for DHW, cooking, dishwasher, laundry, air con, charging the car - but I’ve still got plenty left!
which is why I asked the original question.
I’m basically a tight bastard.

thats sort off what i am trying to achieve by my suggestion to you 'the maximum saving to keep it simple lets assume the total capacity is 5ah[assume 230v] now use it on electrics thats around 1.150w at 230v so 42p
where as iff heated by gas would be around 14p so wasted 28p so even if you can only use half the output on true electrical load you will still be better off 21p rather than the 14p possible replacing gas

now its extremely over simplistic and doesnt allow for gas losses or electrical transmission and conversion loses but a rough idea

 

[JohnW2]

thats sort off what i am trying to achieve by my suggestion to you 'the maximum saving to keep it simple lets assume the total capacity is 5ah[assume 230v] now use it on electrics thats around 1.150w at 230v so 42p ... where as iff heated by gas would be around 14p so wasted 28p so even if you can only use half the output on true electrical load you will still be better off 21p rather than the 14p possible replacing gas

in addition to that .... I never seem to see (but would like to see) is what the 'cost saving' calculations would look like if one factored in paying for the capital cost ) of PV, batteries, fancy control systems etc.) over a period of a few years.

I realise that their are considerations of things other than (monetary) cost saving, but they are presumably not in the forefront of the minds of those who primarily write about, and calculate/estimate, thopse 'cost savings'.

Kind Regards, John

 

[StephenStephen]

Your £1000 gas bill - is that for a year or a month?

 

[petercoupe]

Your £1000 gas bill - is that for a year or a month?

6 months

 

[JohnD]

The winter period, no doubt.