Solar PV calculator 2026: what your German rooftop system earns
A 10 kWp system in Cologne earns €1,220 a year and pays for itself after 12.3 years if it costs €15,000. Work out your own roof.
Checked by Radif Partners · Editorial policy · How we calculate
Benefit per year
€1,220
10,291 kWh of solar power · payback 12.3 years
| Generation per year | 10,291 kWh |
|---|---|
| used at home | 1,578 kWh · 15 % |
| fed into the grid | 8,428 kWh |
| curtailed (60% limit) | 286 kWh |
| Saving on bought power | €571 |
| Feed-in tariff (7.70 ct/kWh) | €649 |
| Benefit per year | €1,220 |
| Payback | 12.3 years |
| Net gain after 20 years | €9,400 |
Step-by-step calculation
- Postcode 50667 (area of Köln): 1,038 kWh per kWp at 35° south (PVGIS); for your direction and 30° tilt 1,029 kWh per kWp.
- Self-consumption from the quarter-hour simulation of 74 households (4,000 kWh): 15 %.
- Without a smart meter the system may feed in at most 60% of its rated output (section 9(2) EEG, commissioned from 25 February 2025).
- Rate for commissioning 1 August 2026 to 31 December 2026, weighted by capacity: 7.70 ct/kWh, fixed for 20 years.
- Negative prices: without a smart meter small systems keep their payment (section 51(2) EEG).
Estimate based on average weather 2005 to 2023 (PVGIS) and metered household loads. A single year can differ by a few per cent. How we calculate
This rooftop PV calculator combines three things that quote-driven calculators usually keep apart. First, the yield at your own location: the European Commission's PVGIS value for your postcode, converted to your tilt and direction, which in Cologne is 1,029 kWh per kWp at 30° south. Second, self-consumption from a quarter-hour simulation with 74 metered German households: of the 10,291 kWh from a 10 kWp system, a household using 4,000 kWh uses 15 % itself, or 31 % with an 8 kWh battery. Third, the rules for systems commissioned from 1 August 2026: a feed-in tariff (Einspeisevergütung) of 7.70 ct/kWh up to 10 kWp, a little less above that, feed-in capped at 60 per cent of rated output without a smart meter, and no payment at negative wholesale prices with one. The benefit is the saving on your bill plus the feed-in payment; payback is the price divided by that benefit.
What the calculator works out
From the postcode, the calculator reads the PVGIS yield of a system tilted 35° to the south and converts it to your roof pitch and orientation; an east-west roof counts as half east, half west. It then simulates every quarter-hour of a year: home first, then battery, then grid. For systems commissioned from 25 February 2025 without a smart meter, feed-in is capped at 60 % of rated output (section 9(2) EEG): whatever exceeds it and is neither used nor stored is lost.
The payment is the rate for your commissioning period according to the Federal Network Agency, weighted by capacity. Tax does not come into it for systems up to 30 kWp per dwelling: the income is exempt from income tax (section 3 no. 72 Income Tax Act) and no VAT is charged on purchase and installation (section 12(3) VAT Act).
The Cologne example
| no battery | with 8 kWh battery | |
|---|---|---|
| Output | 10,291 kWh | 10,291 kWh |
| Used at home | 1,578 kWh (15 %) | 3,230 kWh (31 %) |
| Fed in | 8,428 kWh | 6,783 kWh |
| Lost to the 60% cap | 286 kWh | 278 kWh |
| Benefit per year | €1,220 | €1,692 |
| Cost (assumed) | €15,000 | €21,000 |
| Payback | 12.3 years | 12.4 years |
The battery almost doubles the self-used power, but each stored kilowatt-hour only earns the gap between your electricity price and the feed-in tariff. Whether it pays depends on its price; the home battery calculator works that out separately. The costs are assumptions: enter your quote, because prices per kWp vary a lot by roof, region and equipment.
Limits of the calculation
Shading from dormers, chimneys or trees is not included; an hour of shade at midday costs more than in the morning. A heat pump or electric car shifts consumption, and the households metered in 2010 hardly had either. If you plan one, enter a higher consumption and check the result with the sizing calculator. As for the rules from 2027: the bill has not been passed, so the current EEG 2023 applies here; what is planned is under feed-in tariff 2027.