Solar Yield Calculator
Estimate annual solar energy output for any location using official EU satellite radiation data.
Example: A 5 kWp south-facing system at 35° tilt in Rome (lat 41.90, lon 12.49) produces roughly 7,100 kWh/year — enough to cover the annual electricity consumption of an average Italian household. The same system in Oslo (lat 59.91, lon 10.75) yields around 4,800 kWh/year.
EU JRC PVGIS v5.3, PVGIS-SARAH3 (2005–2023)
How solar yield is calculated
This calculator uses the EU Joint Research Centre Photovoltaic Geographical Information System (PVGIS), a freely available service that provides solar irradiance and PV yield estimates based on satellite radiation data. For Europe and Africa, it uses the PVGIS-SARAH3 database, derived from satellite measurements spanning 2005–2023. The core calculation multiplies the in-plane irradiation (the solar energy per square metre falling on the panel surface, adjusted for tilt and orientation) by the system rated power and the performance ratio to give the annual energy yield in kilowatt-hours.
The performance ratio is the fraction of theoretical maximum yield that the system actually delivers, accounting for temperature losses, inverter efficiency, wiring losses, soiling, and shading. A well-maintained system typically achieves a performance ratio of 75–85%. The specific yield (kWh per kWp) allows direct comparison between systems of different sizes: a higher specific yield means the location or configuration is making better use of the available solar resource. See the Solar Panel Savings Estimator to turn this yield into estimated bill savings.
Frequently asked questions
- What is PVGIS?
- PVGIS (Photovoltaic Geographical Information System) is a free tool and database developed by the EU Joint Research Centre. It provides solar irradiance data derived from satellite measurements and climate models, covering Europe, Africa, Asia, and the Americas. It is widely used by engineers, planners, and researchers for solar energy assessments.
- What does kWp mean?
- kWp (kilowatt-peak) is the rated power of a PV system under Standard Test Conditions (STC): 1000 W/m² irradiance, 25°C cell temperature, AM1.5 spectrum. A typical residential solar panel is 300–450 Wp, so a 5 kWp system has about 12–17 panels.
- What tilt angle and orientation should I use?
- In Europe, south-facing panels at a tilt angle equal to your latitude minus 10–15° typically maximise annual yield. For example, a site at 52° latitude (central Europe) would use around 35–40° tilt. Flat roofs (0° tilt) lose around 10–20% compared to the optimal angle; east/west splits on flat roofs can improve self-consumption profiles.
- What does performance ratio mean?
- The performance ratio (PR) is the ratio of actual energy output to the theoretical maximum if the system operated at its rated power for every hour of available irradiation. A PR of 0.80 means 80% of the available solar energy is converted to usable electricity. Typical values are 0.70–0.85. Lower values indicate higher losses from heat, shading, or equipment.
- How accurate are these estimates?
- PVGIS estimates are validated against measured ground data and typically agree within ±5–10% for well-sited systems in Europe. Accuracy is lower in areas with complex terrain, frequent fog, or heavy snow cover. The estimates represent a long-term annual average — actual output in any given year can vary by ±10–15% due to weather variability.
- Can I use this in my own application?
- Yes — every calculator on Stupidly Clever has a matching REST API and MCP tool that runs the same underlying logic.