The combination of heat pump and photovoltaics is one of the most economical investments for homeowners in 2026. A properly sized PV system can cover 40–60% of the electricity demand of a heat pump directly from solar energy. Together with KfW funding for both technologies, the investment often amortizes in less than 8 years.
The Most Important Points at a Glance
- PV system 8–12 kWp recommended for single-family home with heat pump
- 40–60% of heat pump electricity can be covered by solar
- Surplus control and smart home integration maximize self-consumption
- KfW 270 funds PV systems additionally with low-interest loans
- Electricity storage increases solar share to up to 70%
Why the Combination is Ideal
Heat pumps and photovoltaics complement each other perfectly: The heat pump is an electricity-based heat generator, and the PV system produces cost-free electricity. The clou: Both technologies are funded by the state, and the combination dramatically lowers the operating costs of the heat pump.
Without PV system, a heat pump pays the full electricity price of currently about 30 cents/kWh. With solar power from your own system, this effective price drops to the production costs of about 8–12 cents/kWh for the self-generated portion.
Sizing: How Large Should the PV System Be?
The right size of the PV system depends on the electricity consumption of the heat pump and the remaining household consumption:
| House Type | HP Electricity Demand | Recommended PV Size | Solar Share |
|---|---|---|---|
| SFH well insulated (120 m²) | 4,000–5,000 kWh/year | 8–9 kWp | 50–60% |
| SFH medium (150 m²) | 6,000–7,500 kWh/year | 9–12 kWp | 40–50% |
| SFH old building (150 m²) | 8,000–10,000 kWh/year | 12–15 kWp | 30–40% |
The optimal PV size results from the ratio of annual electricity consumption to annual yield. In Germany, 1 kWp produces about 900–1,100 kWh of electricity per year (depending on region). A 10-kWp system in southern Bavaria delivers about 11,000 kWh, in northern Schleswig-Holstein about 9,000 kWh.
Surplus Control: Using Solar Power Intelligently
The greatest potential lies in the intelligent use of PV surplus. When the sun is shining and the system produces more electricity than the household consumes, this surplus electricity should drive the heat pump:
SG Ready: The Intelligent Heat Pump
Many modern heat pumps have an SG-Ready interface (Smart Grid Ready). This enables control via an energy management system (EMS) that recognizes PV surplus and automatically activates the heat pump.
Smart Home Solutions
Alternatively, smart home systems like Home Assistant, ioBroker, or commercial solutions from SolarEdge, Fronius, or SMA can activate the heat pump with PV surplus. The heat pump then heats the buffer storage or hot water tank to a higher temperature level and stores the energy thermally.
Example Calculation with PV System: SFH 150 m²
Heat pump consumption: 7,500 kWh/year
PV system 10 kWp: Yield ~10,000 kWh/year
Self-consumption share (without HP control): 35%
With surplus control: 55% self-consumption
Heat pump electricity costs without PV: 7,500 × €0.30 = €2,250
With PV (55% solar at 10 cents/kWh, 45% grid purchase at 30 cents/kWh):
4,125 × €0.10 + 3,375 × €0.30 = €412 + €1,012 = €1,425
Savings: €825/year alone through PV usage
Plus: Feed-in tariff for surplus PV electricity (8.11 cents/kWh 2026)
Does an Electricity Storage Pay Off?
A battery storage (5–10 kWh) increases the self-consumption of the PV system from about 35% to 60–70%. For the heat pump, this means: More solar power, less grid purchase. However, a storage costs an additional €5,000–10,000.
Recommendation: If you're planning a new PV system anyway, integrate the storage from the start. The KfW funding for solar + storage offers low-interest loans, which accelerates amortization.
Calculate Your Combination Now:
Funding: PV + Heat Pump Combined
Both technologies are funded separately:
- Heat pump: KfW 261, up to 70% grant on purchase costs
- Photovoltaics: KfW 270, low-interest loans from 3.5% effective annual interest
- Electricity storage: Partially fundable via KfW 270
- EEG feed-in tariff: 8.11 cents/kWh for surplus feed-in (2026)
Note: The photovoltaics feed-in tariff is guaranteed for 20 years. This makes the PV system, in addition to heat pump optimization, a secure investment.
Frequently Asked Questions About Heat Pumps with Photovoltaics
Can my existing heat pump be connected to a retrofitted PV system?
Yes, in most cases. Many heat pumps have a potential-free contact input (S0 interface or SG-Ready). Via an energy management system like Home Assistant, SMA Sunny Home Manager, or SolarEdge, the heat pump can be automatically switched on with PV surplus. Older models may need an external control module.
How large should the buffer storage be for PV surplus usage?
For effective PV surplus usage, a buffer storage of at least 300–500 liters is recommended. This allows the heat pump to convert surplus electricity into heat when the sun is shining and store it for the night. Larger buffers (750–1,000 liters) are ideal for larger systems.
What does a PV system with heat pump cost together?
A 10-kWp PV system costs about €12,000–18,000 (incl. inverter and installation). Together with a heat pump (from €15,000), total costs of €27,000–43,000 are realistic. With funding (KfW 261 for HP + KfW 270 for PV), net costs can drop to €15,000–25,000.
Does a photovoltaics system amortize for the heat pump?
Yes, the combination usually amortizes in 8–12 years. The PV system saves electricity costs (approx. 20–30 cents/kWh saved grid purchase) and additionally generates feed-in tariff for surplus electricity. At a system price of €1.20–1.80 per Wp and 900–1,100 kWh/kWp annual yield, the return is attractive, even without a heat pump.
Do I need a permit for the PV system?
A PV system on the roof must be registered with the Federal Network Agency in the Market Master Data Register. For systems up to 30 kWp, no building permit is required. For listed buildings or special locations, however, the municipality may impose requirements. A balcony power plant (up to 2 kW) is permit-free and only needs to be registered.