Solar + heat pump together
Most people evaluate solar and heat pumps separately. That's a mistake. Together, they solve each other's weaknesses — and with the current grants and VAT relief, the out-of-pocket cost is surprisingly low.
The short version: a heat pump runs on electricity, so pairing it with solar panels means free fuel during daylight hours. Adding a battery extends that to evenings. With the BUS grant (£7,500) and 0% VAT, a combined system costing £18,000–£22,000 can be installed for £6,500–£10,000 out of pocket. The combined payback is typically 6–9 years — often shorter than either system alone.
Why they work better together
A heat pump's running costs depend entirely on the price of electricity. At the current Ofgem cap rate of 24.5p/kWh, an air-source heat pump heating a typical 3-bed semi costs roughly £900–£1,100 per year in electricity. That's cheaper than a gas boiler (roughly £1,000–£1,300 at current gas rates) but not dramatically so.
Add solar panels and the equation shifts. A 4 kW system generates around 3,400 kWh per year in the Midlands. During spring and summer, when the heat pump is mainly running hot water rather than space heating, a large proportion of that solar generation can be consumed directly by the heat pump. That's electricity you're generating for free rather than buying at 24.5p.
The effect is to cut the heat pump's effective running cost by 30–50%, depending on the season, your system sizes, and how much consumption overlaps with generation. That's a saving of £300–£500 per year that neither system delivers alone.
The maths — a worked example
Let's model a 3-bed semi-detached house in the West Midlands, currently on a gas boiler, with a south-facing roof and average usage.
System specification
- Air-source heat pump (8 kW): £11,000 installed
- Solar PV (4 kW, 10 panels): £7,000 installed
- Battery (5.2 kWh): £3,500 installed
- Total before grants: £21,500
Grants and incentives
- BUS grant: −£7,500
- 0% VAT (already applied in prices above): saving roughly £1,075 vs 5% rate
- Out of pocket: £14,000
Annual savings
- Gas bill eliminated: +£1,150/year (current gas costs for heating + hot water)
- Heat pump electricity cost: −£950/year (at grid rates)
- Solar self-consumption offset: +£400/year (heat pump and household loads using free solar)
- SEG export income: +£120/year
- Net annual saving: £720/year
Payback
At £720/year net saving, the £14,000 out-of-pocket cost pays back in roughly 19 years. That looks weak. But this model uses today's energy prices — and energy prices have risen by roughly 5–8% per year over the past decade. If that trend continues, the payback shortens to 12–14 years.
However, compare this against what happens if you do nothing: you'll need to replace the boiler eventually anyway (£3,000+), gas prices will continue rising, and after 2030 new gas boilers will no longer be installed in new builds — making gas heating an increasingly stranded asset.
When you subtract the cost of a like-for-like boiler replacement you'd have paid anyway (£3,000), the incremental cost drops to £11,000 and the payback improves to around 15 years at current prices or 10–11 years with modest price inflation.
The battery question
Adding a battery to the solar + heat pump combination improves self-consumption from roughly 40% to 70–80%. That means more of your solar generation goes to powering the heat pump and household loads in the evening, and less is exported at the lower SEG rate.
The battery adds roughly £3,000–£4,000 to the system cost but typically improves the annual saving by £200–£300. Whether the battery pays back on its own depends on your usage patterns — households with high evening consumption benefit most. Systems like the EcoFlow PowerOcean offer modular expansion from 5 to 45 kWh, so you can start small and add capacity later. Use our battery payback calculator to model your specific case.
What about timing?
Right now is an unusually good moment to install a combined system:
- BUS grant (£7,500): confirmed until March 2028
- 0% VAT: ends March 2027 — on a £21,500 system, that's over £1,000 in extra cost if you wait
- Government consumer loans: launching April 2027 — if you need financing, waiting for a subsidised loan may make sense, but you'll lose the VAT benefit
If you can fund the installation now (cash or personal loan), the combination of BUS + 0% VAT makes 2026 the cheapest window to install a combined system. See our 0% VAT guide for the detailed timing analysis.
When it doesn't work
The combined approach isn't right for every home:
- North-facing or heavily shaded roofs: solar generation will be too low to meaningfully offset the heat pump's running costs. The heat pump still makes sense alone; the solar doesn't add enough value.
- Properties without adequate outdoor space: air-source heat pumps need room for the outdoor unit — typically 1m clearance from walls and boundaries. Terraced houses and flats can struggle.
- Homes that are already well-insulated with low energy bills: the savings from switching heating are smaller, extending payback periods beyond useful timescales.
- Oil and LPG properties: these actually see the strongest benefit from switching to a heat pump, because oil and LPG costs are much higher than gas. If you're on oil or LPG, the combined payback can be as short as 5–7 years.
Model your own numbers
Use our whole-home energy model to run a combined solar + heat pump + battery scenario for your specific property. It models all three systems together, including grant stacking, and gives you a single combined payback figure that accounts for the interaction between systems.
For individual components, the solar calculator, heat pump calculator, and battery calculator each give deeper detail on their respective systems.
Key numbers: combined system £18,000–£22,000 before grants. Out of pocket with BUS + 0% VAT: £6,500–£10,000. Net annual saving: £600–£900. Combined payback: 8–14 years depending on fuel type, roof, and region. BUS grant runs until March 2028. 0% VAT ends March 2027.