Methodology
Every Energravia report is a model calculation based on public, citable data sources. This page explains how we calculate — so you can justify every number to your customers.
Data sources
Solar yields come from PVGIS (EU Joint Research Centre), wind resources from the Global Wind Atlas (DTU/World Bank), electricity prices from Eurostat and the ENTSO-E spot market, heat-pump climate data from Copernicus. All sources are linked on the data sources page.
Solar calculation
Annual yield from PVGIS per location, azimuth and tilt; minus location-specific soiling losses and, in Germany, the 60% feed-in power cap without an intelligent metering system. Degradation: 0.5% per year, compounded. P90 values are based on inter-annual yield variability (EMHIRES).
Wind calculation
Annual yield = capacity factor × rated power × 8760 h, corrected by −10% per the NREL (2022) validation of Global Wind Atlas data. A P80 band is shown.
Economics
Annual benefit = self-consumption savings (retail price) + feed-in revenue (EEG rate or spot-market mean) − operating costs. Payback: first year in which cumulative benefit covers the investment. NPV at 3% discount rate (adjustable). Electricity price scenarios: +2/+4/+6% p.a. as a band. Battery storage: hourly charge/discharge simulation over 8760 hours with a BDEW H0 load profile.
Regulatory assumptions (Germany)
EEG feed-in rates by system size and full/surplus feed-in incl. half-yearly degression (Feb 1 / Aug 1). Solarspitzengesetz: loss of remuneration during negative price hours is modeled as a configurable revenue discount on feed-in. All values are versioned with source and as-of date and shown in the report.
Heat pump comparison
COP derived from climate (heating degree days) and typical manufacturer COP curves; compared against a gas boiler (87% efficiency) over 20 years incl. price escalation paths. Subsidy notes (BEG) are reference values — binding assessment by an energy consultant/BAFA required.
Update cadence
Time-critical values (EEG rates, electricity price defaults, regulatory thresholds) carry a review date and are monitored via an internal registry: values older than 90 days automatically trigger a review. Every report shows the as-of date of the data basis used.
EEG rates last reviewed: 2026-07-04. All information without guarantee — no tax, legal or financial advice.