Can Solar Panels Run a Heat Pump?

It’s one of the most common questions we get on a survey, and it usually arrives with a hopeful tone: if the heat pump runs on electricity, and the panels make electricity, can the roof just power the heating?

The honest answer is partly — and the part it covers isn’t the part most people assume. Here’s how the two actually fit together.

The seasonal mismatch is the whole story

A heat pump uses most of its electricity in December, January and February. A solar array generates least in December, January and February — perhaps 3–5% of its annual output in each of those months.

Put numbers on it. A well-sited 4.4kWp system in the North West generates around 3,400–3,900 kWh a year, but in deep winter that’s roughly 3–6 kWh on an average day. A heat pump heating a typical three-bed through a cold snap might draw 15–25 kWh a day. The panels are contributing something, but they aren’t carrying the heating.

Any installer who tells you solar will “run your heat pump” through winter is either not thinking it through or hoping you won’t.

What solar genuinely does cover

That’s not the end of it, because a heat pump doesn’t only heat radiators.

Hot water, almost all year. Producing your hot water is a small, daily, predictable load — and from roughly April to September a modest array covers it comfortably. Set the cylinder to reheat in the early afternoon rather than at 6am and you’re making hot water on free electricity for half the year.

The shoulder seasons. March, April, October and early November are the sweet spot: real heating demand, and real generation to meet it. A heat pump running gently at a low flow temperature through a mild spring day is often drawing exactly what the roof is producing.

Everything else in the house. This is the point people miss. Adding a heat pump roughly doubles a typical home’s electricity consumption — from around 3,500 kWh a year to 6,000–8,000 kWh. That doesn’t make solar less worthwhile; it makes it more worthwhile, because a bigger baseload means far less of your generation gets exported at Smart Export Guarantee rates of around 12p and far more of it displaces grid units at around 24p. The same panels earn roughly twice as much in a heat pump home.

Where the battery and the tariff come in

The combination that actually works in a UK winter isn’t solar alone — it’s solar, storage and the right tariff working together.

Heat pump tariffs price overnight and off-peak electricity far below the standard rate. A battery lets you buy the winter’s heating electricity at those cheap rates, then run the house and the heat pump from storage through the expensive evening window. In summer, the same battery soaks up the surplus your panels make while nobody’s home and pushes it back into the evening’s hot water and cooking.

Batteries stack from 5 kWh up to 60 kWh, so sizing follows the load rather than the other way round. Homes with a heat pump usually want more capacity than a solar-only household — there’s simply more electricity moving through the house to shift.

Sizing the array for a heat pump home

Two practical points from surveys:

• Don’t size the array to the heat pump’s winter demand. You’d need an implausible roof, and it still wouldn’t work on a dark January day. Size it to your annual consumption and the roof you actually have — typically 6 to 20 panels at 460W each.
• Fit the panels at the same time if you can. Scaffolding, notification to the network operator and a single visit from one team is cheaper and less disruptive than two separate projects a year apart. The heat pump grant is handled the same way either route: £7,500 off an air source system, £9,000 if you’re off the gas grid on oil or LPG, claimed by us rather than by you.

The straight version

Solar won’t run your heat pump through a cold January. It will run your hot water for half the year, cover a good share of shoulder-season heating, and — most importantly — a heat pump makes every panel on your roof work harder by giving that generation somewhere useful to go.

If you’re weighing up one, the other, or both, our survey is free and there’s no obligation. We’ll model the two together properly, including the lean months, and tell you honestly which order makes sense for your house.