Comparison · 7 min read · Updated 2026-05-08
Solar PV + heat pump — economics in 2026
Combining rooftop PV with a heat pump can move the payback math from marginal to obvious. The self-consumption ratio, battery sizing and how subsidies stack.
The simple version
A heat pump runs on electricity. Rooftop solar produces electricity. The fraction of HP demand you can self-supply from the roof is the lever that determines whether HP economics tip from marginal to obvious — especially in countries where retail electricity is far more expensive than gas (DE, BE, IE).
The hard part: when does the HP run?
Solar peaks midday in summer. A heat pump peaks early morning and evening, in winter, when solar produces almost nothing.
Without storage, the natural overlap between PV output and HP consumption is around 15–25% for a typical European single-family home. Most HP electricity in winter still comes from the grid.
Three levers that improve overlap
1. Inertia — buffer cylinder + thermal mass
A 200–400 L buffer cylinder lets you time-shift HP operation. The HP runs 11:00–15:00 from solar, charges the buffer and the underfloor slab, then coasts through evening peak. Extra capex: €1500–3000. Self-consumption rises to 35–50%.
2. Battery storage
A 5–10 kWh home battery captures unused midday solar and discharges to the HP at night. Capex €4–10k. Self-consumption rises to 65–80%. Longer payback because batteries are still expensive per kWh of turnaround capacity.
3. Smart control
Modern HPs and inverters integrate (S-Net, EEBUS, ModBus). The HP modulates its output upward when PV exports would otherwise be clipped, downward when grid prices spike. Adds 5–10% self-consumption without hardware cost; needs an inverter and HP that speak the same protocol.
Payback math: a worked example
A 150 m² home in Germany, 18 000 kWh annual heat demand, SCOP 4 → 4 500 kWh of HP electricity per year. With:
- 8 kWp PV producing 8 000 kWh/yr at €0.22/kWh installed cost
- 50% HP self-consumption thanks to buffer cylinder
- HP capex €18 000, BEG subsidy 70% → €5 400 net
- PV capex €12 000, no subsidy
- Grid: €0.39/kWh import / €0.08/kWh export
| Item | Without PV | With PV (50% self-cons.) |
|---|---|---|
| HP grid kWh | 4 500 | 2 250 |
| HP grid cost | €1 754 | €877 |
| Self-consumed PV (used by HP) | 0 | 2 250 kWh |
| Surplus PV exported | 0 | ~6 000 kWh × €0.08 = €480/yr offsetting bill |
| Combined annual heating cost | €1 754 | €397 |
| Annual saving from PV | — | €1 357 |
PV pays back in ~9 years if treated as part of the HP project. Without HP loading, PV alone in DE pays back in 13–15 years.
How subsidies stack
Whether HP and PV grants combine depends on country:
- Germany BEG — HP grant only; PV gets KfW low-rate financing
separately. Stack-friendly.
- France MaPrimeRénov' — HP only; PV through CEE certificates.
- Italy Conto Termico — HP only; PV through Ecobonus (50% tax
credit, separate envelope).
- Poland Czyste Powietrze — HP up to 100%, PV under
Mój Prąd. Both apply if you separately qualify.
When the math doesn't work
PV + HP economics depend on electricity-to-gas price ratio. In countries where gas is cheap and electricity expensive (DE, IE, BE), PV is the multiplier that flips it. Where electricity is already cheap (HU, BG, FR), HP alone is competitive and PV is a nice-to-have, not a tipping point.
For your numbers, run the payback calculator with the realistic post-PV electricity price and SCOP 4.0+.