← All guides · 2026-07-03
How Accurate Is PVGIS? What the Research Says
What PVGIS actually is
PVGIS is the European Commission Joint Research Centre's free PV simulation service, used millions of times a year. It combines satellite irradiation databases (SARAH3 for Europe, Africa and much of Asia; ERA5 reanalysis elsewhere) with a physical PV performance model covering temperature, incidence-angle and spectral losses. Sunveyor uses the PVGIS 5.3 engine for its production simulations.
Measured accuracy
Validation studies comparing PVGIS estimates against metered rooftop and utility systems consistently find annual production errors within ±4–8% for well-characterised systems in satellite-covered regions. Monthly errors are larger (±10–15%, worst in winter). The biggest error source is rarely the model — it is wrong user inputs: real shading, soiling, actual system losses and inverter clipping that defaults don't capture.
Known biases to keep in mind
SARAH3 slightly overestimates irradiation in some coastal and high-mountain zones and underestimates under persistent fog. ERA5-based estimates (used where satellite data is unavailable) carry roughly double the uncertainty of SARAH3. Snow losses are not modelled by default, which matters above ~45° latitude. And the default 14% system loss is honest for new systems but optimistic for ageing ones.
Free estimate vs bankable study
For household decisions and pre-feasibility screening, PVGIS-class accuracy is more than sufficient — the ±5% band is smaller than a single year's weather swing. Banks financing multi-megawatt plants demand more: P50/P90 yield assessments built on 1–2 km satellite data with on-site measurement campaigns, from providers like Solargis or SolarAnywhere, costing thousands of dollars. The rational path: screen free, verify the shortlist, pay for bankability only on the finalist site.
Click your location on the satellite map and get irradiation, 40-year history and a production simulation — free.
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