Using solar PV to heat your domestic hot water
Posted by Paul Hutchens on 26 May 2011 at 10:25 am
Q: Having recently installed Solar PV, I will soon be replacing our old boiler and hot water cylinder. The heating and water run on gas. Does it now make sense to use electricity to heat the hot water for the house?
A: This is a really interesting conundrum - well I think it is - but maybe I am a dull solar enthusiast! Nevertheless I will try to purvey my passion in my answer.
The thing is that mains gas is much cheaper and has a lower carbon footprint than electricity. In addition to that, we in the UK have spent the last 40 years transforming our energy usage away from other fuel sources to gas if we can – remember the 'dash for gas' in the seventies – because we have had the luxury of cheap gas from the North Sea.
The bad news is that this is now running out and by about 2015 we will be importing around 90% of our gas from Russia and the Middle East.
So guess what will happen now - that’s right prices are rising and will continue to rise. So maybe gas will not continue to be the cheap alternative that we have all got so used to.
From an environmental perspective our calculations and assessments assume that electricity comes from stinky, dirty coal and gas fired power stations. What if the electricity that we used was zero carbon?
What if that electricity came from our own, on site solar powered electricity or PV system?
We would then be provided with a free and zero emissions way of powering things – such as an immersion heater.
There is another benefit too. We all know - or you should by now if you read the YouGen blogs regularly which I am sure you do – that you get paid for all the electricity you use from the feed-in Tariffs. Excellent!
You produce free electricity too, for which – on average for a domestic consumer – you would have paid about 15p per unit from your energy supplier. If you cannot use it you export to the grid and get 3p per unit instead. Well I am no mathematical genius but I can work out without the aid of a calculator which I would rather do.
So what to do with the excess' electricity to maximise our investment? How about using to power your immersion heater and store the energy in the form of hot water than you can use later to bathe or shower with?
I am not sure that you would want to completely replace the connection to your boiler – in the winter or when it is dark you may be glad of it. But wouldn’t it make sense to top it up with free electricity when it is available?
You can also adjust your hot water heating controls to take best advantage of the free energy. Your installer can advise you about this to ensure that you get the best out of the solar power without ending up with a cold shower!
Photo by Ged Carroll
More information about using your solar PV electricity on YouGen
If you have a question about anything in the above blog, please ask it in the comments section below.
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