Heat pumps and solar — do they work well together?
How a heat pump changes your electricity use and what that means for sizing a solar system.
Heat pumps use electricity to produce heat — which changes the electricity demand picture significantly. If you have a heat pump or are considering one, here is what that means for solar.
Why a heat pump changes the solar maths
A typical air source heat pump in a well-insulated UK home might use 3,000–6,000 kWh of electricity per year for heating. That is a material addition to a household's electricity demand — and it changes the sizing conversation. A solar system designed before a heat pump is added may be undersized once the heat pump is running.
When does solar overlap with heat pump demand?
The good news is that heat pumps do much of their work in winter, when solar generates less. In spring and autumn there is more overlap — milder weather means less heating demand, and there is reasonable solar generation. Smart heat pump controllers can shift heating runs to match solar generation, which helps.
Sizing considerations
If you have — or plan to have — a heat pump, tell the installer (and our Solar Check). A heat pump typically adds 1–2 kWp to the sensible system size. Whether that is worthwhile depends on your roof space, your heat pump usage patterns and your electricity tariff.
Heat pumps and hot water
Heat pump hot water cylinders (also called heat pump water heaters or immersion diverters) can absorb surplus solar electricity during the day to heat a hot water cylinder. This is a cost-effective way to use generation that would otherwise be exported, without needing a battery.
Key takeaways
- A heat pump adds significant electricity demand — tell your installer and include it in any Solar Check.
- Most heat pump demand is in winter, when solar generates least — the overlap is modest but real.
- Smart controllers can shift heat pump runs to match solar generation.
- A hot water cylinder with an immersion diverter is a low-cost way to use surplus solar without a battery.
This guide is for general information only. It is not a substitute for a survey of your home or professional advice. Solar Help Centre does not install solar equipment or produce the final design for your home.
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