German Weather Service (DWD), average 1991–2020: Germany 1,086 kWh/m², 975–1,259 kWh/m² depending on location (on a horizontal surface). DWD radiation maps show the value for your location; tilted south-facing roofs usually receive a little more, east/west roofs less.
Performance ratio (PR)
The performance ratio sums up all system losses (inverter, temperature, shading, cabling). 80% is our assumption, not a standard – your installer or data sheet gives the value for your system.
Gross; for systems up to 30 kWp on or near residential buildings VAT is 0% (Section 12(3) UStG)
From your electricity bill, cents per kWh
Feed-in
Your assumption; without storage usually well under half, higher with storage
Insurance, maintenance, meter rental – your figures
Annual solar yield
8,688kWh
8,688A 10 kWp system produces around 8,688 kWh a year at 1,086 kWh/m² irradiation and a 80% performance ratio – 869 kWh per kWp.
Yield = capacity × irradiation ÷ 1 kW/m² × performance ratio (IEC 61724-1). Irradiation divided by the standard irradiance of 1 kW/m² gives the hours of full sun; the performance ratio deducts the system losses. The result per kWp is also called full-load hours.
For the calculation we need your quoted price and your electricity price – we do not quote market prices.
Income from systems up to 30 kWp per residential or commercial unit on or at buildings is exempt from income tax (Section 3 no. 72 EStG, with a cap per person).
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