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Will my solar panels power an air source heat pump?

Posted by Cathy Debenham on 27 May 2014 at 8:54 am

Q: I have a 4kW solar PV system on my roof and am thinking of installing an air source heat pump. How much electricity would the solar panels contribute to the cost of running the heat pump?

A: At first glance this seems like the ideal combination. You are probably generating more solar elecricity than you can use. Why not use some of it to offset the heating bills? 

But, and it's a big but, the timings are not compatible. Solar systems generate the vast majority of the electricity between March and September. The months you need most of your heating are October to March. As you see, that doesn't leave much overlap.

In winter, what little solar generation there is will be in the middle of the day. Most of the domestic heating is needed in the morning and evening - so even less of an overlap.

Of course, you can use the income from the feed-in tariff to contribute to the cost of running an air source heat pump. But don't kid yourself that it means you are using free, clean electricity to do it.

The Centre for Alternative Technology's Toby Kellner was asked at the Sustainable Homes Show what an ideal set up for a heat pump would be. His dream system would be in the Hebrides: a thoroughly insulated house, with underfloor heating and a wind turbine (the wind blows all year) to power a heat pump.

Photo: London Permaculture


If you have a question about anything in the above blog, please ask it in the comments section below.

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2 comments - read them below or add one

Cathy Debenham

Cathy DebenhamComment left on: 9 March 2015 at 11:12 am

@sdeleng This blog was written for those of us who spend our winters under gloomy, grey British skies, so I imagine that your situation will be quite different.

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sdelengComment left on: 6 March 2015 at 12:30 pm

But if you have a massive bank of batteries, surely this does not matter?  They willl work all night.  I live in Spain and my panels charge more in the winter than the summer as it is not as hot, but just as sunny.  I am really interested in an answer to this.

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