Calculation methodology
Transparency is important to us. Here we explain all calculations and their foundations.
Solar irradiation is based on data from the PVGIS system (Photovoltaic Geographical Information System) of the European Commission's Joint Research Centre. PVGIS uses satellite data and meteorological models for accurate site assessment.
PV yield is calculated directly from PVGIS data, which already accounts for location, tilt, orientation, and system losses (14%). An additional shading factor is applied.
The self-consumption ratio is estimated using the HTW Berlin model (Quaschning/Weniger). It is based on the BDEW H0 standard load profile for household electricity. For battery storage, the additional self-consumption increase is calculated with a battery efficiency of 90%.
The financial analysis is based on the following assumptions:
- Electricity price: 0.3436 €/kWh (increase: 3% p.a.)
- Feed-in tariff: per EEG (fixed for 20 years)
- Module degradation: 0.5% per year
- Maintenance costs: 1.5% of investment per year
- Discount rate: 3% (for NPV calculation)
This tool does not consider: local shading from objects, roof statics and load capacity, grid connection conditions, regional/municipal subsidy programs, tax aspects.