Solar panels and a heat pump together: does it make sense?

Yes, almost always. A heat pump is the single best appliance to pair with solar panels because it converts cheap (or free) electricity into heat at 3-4× efficiency. A typical UK home running both saves £400-£800/yr on top of either system on its own.

Here is what to think about before committing.

How they actually combine

The summer half of the year is when solar generates most. It is also when your heat pump runs least — only producing hot water, not space heating. So summer-generated solar electricity goes straight into hot-water cycles, displacing grid imports.

The winter half of the year is when your heat pump runs hardest. Solar still generates (about 30-40% of summer output) and offsets some of that demand. Combined with a battery, you can also store cheap overnight electricity and use it during the morning heat-up cycle.

The numbers for a typical home

3-bed semi, 4kWp solar array, 6kW heat pump:

• Solar generates ~3,500 kWh/yr.
• Heat pump consumes ~4,000 kWh/yr.
• About 35-50% of solar generation lines up with heat-pump demand (rest is exported or covers other household use).
• Self-consumed solar saves ~£300-£500/yr; exported solar earns ~£100-£200/yr via the Smart Export Guarantee.

Add a 5 kWh battery and you can store more solar for evening use, lifting savings by another £100-£200/yr.

Install sequence — which one first?

If you are doing both within 12 months of each other, do them together:

• One scaffolding visit, one electrician day, one DNO notification.
• The installer can size the inverter and consumer unit for both loads from the start.
• Combined commissioning means smart controls (e.g. solar diverter to the hot water cylinder) work out of the box.

If you can only do one now:

• Heat pump first if your boiler is dying or you want to claim the BUS grant before scheme changes.
• Solar first if your roof needs replacing soon (the panels will outlast the underlying tiles by decades) or you are about to add an EV.

Sizing — getting it right

Your heat pump should be sized to your heat loss, not your solar generation — never undersize the pump to "match" solar. Cold January days are when you need full heat output, and the sun is not generating then.

Your solar array should be sized to fill the available roof area, capped only by your inverter or DNO limits. Most UK roofs accommodate 4-8 kWp without exporting more than the standard G98 limit.

Hot water diversion — the cheap upgrade

A solar diverter (£300-£500 fitted) routes excess solar electricity into the hot water cylinder's immersion element when there is nothing else to consume it. Means almost zero summer electricity cost for hot water.

The heat pump can do the same job more efficiently when the cylinder needs heating — but on bright summer afternoons when the cylinder is already warm, the diverter prevents the energy going to the grid for 5-7p/kWh export rate.

Tariff strategy

With both systems installed, the optimal tariff is usually a time-of-use one (Octopus Cosy, OVO Heat Pump Plus). Set the heat pump to run hot-water cycles during off-peak hours, let solar cover daytime demand, and use a battery to time-shift any remaining gap.

Whole-house running costs for an average 3-bed combining heat pump + solar + battery on a smart tariff: typically £400-£700/yr — a small fraction of the £2,000-£3,000/yr most homes pay on gas + grid electricity.

The bottom line

If you are getting one, plan for both. The marginal cost of adding solar to a heat pump install is ~£5,000-£8,000 net of the inverter you would have needed anyway. Payback is typically 6-9 years and the systems share a 25-year operational lifespan. Run our free pre-survey check to see what a combined install looks like on your roof.