What this tool tells you
Pick a point on the map, set how your panels are mounted, and get a real long-term estimate of how much electricity a rooftop PV array would produce there each year. The numbers come straight from PVGIS, the EU Joint Research Centre's open-data service that fuses satellite measurements (CMSAF SARAH-2, ERA5) with site-specific climate models. PVGIS is what professional installers, utilities and grid planners use to size systems across Europe and most of the world. No API key needed.
The result you get is climatological (a typical year built from 10+ years of recorded weather), not a forecast for next month. That makes it ideal for planning a system: deciding panel count, comparing roof orientations, sizing a battery, and stress-testing a payback period before signing a contract.
Pairs naturally with the STC rating on your panel spec sheet: PVGIS already accounts for real-world losses (panel heat, inverter efficiency, cabling, soiling, shading averages) so the kWh number you see is what should actually hit your meter.
How to use it
- Click anywhere on the map (or drag the marker) to pick a location. Use the sample chips (Warsaw, Berlin, Madrid, Reykjavik) for a quick benchmark before tweaking.
- Set the tilt (slider, 0 to 90 degrees). For most of Europe the optimum is 30 to 40 degrees. Lower if you live near the equator, higher if you live near the poles. Flat roofs default to mounting frames at 10 to 15 degrees to limit wind load and snow build-up.
- Set the azimuth: 0 = north, 90 = east, 180 = south, 270 = west. In the northern hemisphere south-facing wins. East/west splits sacrifice 10 to 15% of annual yield but flatten the daily curve, which can match a home battery better.
- Set the system size in kWp. A typical European single-family home installs 4 to 8 kWp. Each module is roughly 0.4 to 0.5 kWp, so a 5 kWp system is around 10 to 12 panels covering 25 to 30 square meters of roof.
- Hit Calculate. The big number on top is the annual yield in kWh. Underneath you see the specific yield in kWh/kWp (system-size independent, perfect for comparing locations) and the capacity factor.
- The monthly bar chart shows the seasonal shape: in mid-latitude Europe expect roughly 6x more production in June than in December. The chart also tells you which month will be your peak and which will be your worst (handy when sizing a winter battery buffer).
- Copy the full JSON output with the Copy JSON button for piping into your own spreadsheet or for sharing with an installer.
When this is useful
Real situations where a PVGIS yield estimate changes a real decision:
- Comparing two roofs on the same house: you have a south-facing pitch and a west-facing pitch. Run both, look at the kWh delta, and you know whether the west face is worth the extra mounting cost. Spoiler: in most of Europe the south face beats west by 10 to 15%, but for a household that mostly uses electricity in the afternoon and evening, the west face can actually be better because it generates when you actually consume.
- Pre-quote sanity check before talking to an installer: get a baseline kWh number for your address and your roof. When the installer's proposal arrives, check whether their predicted yield matches PVGIS within 5%. If the installer is promising 20% more than PVGIS without explaining why, you have a great question to ask in writing.
- Sizing a home battery: the monthly chart shows you December and January production. Compare against your average winter consumption (electricity bill, kWh column) to see if a small battery (5 to 10 kWh) can carry the day-to-night gap, or whether you need to plan around grid imports during dark months.
- Off-grid cabin / RV / boat planning: PVGIS gives you the absolute floor of what the panels can deliver in the worst month. Size your battery bank against that floor, not against the annual average, or your fridge will die in January.
- Deciding tilt for a ground-mount or flat roof: walk the tilt slider from 10 to 60 degrees and watch how annual yield responds. For 52 degrees north (Warsaw, Berlin, Amsterdam) the curve peaks softly around 35 degrees and stays within 2% from 25 to 45 degrees, so you can pick whatever fits your structural and visual constraints.
- Estimating return on investment: combine the annual kWh number with the wholesale electricity price (see Live Electricity Prices) and your retail tariff to project annual savings. Useful gut-check before committing capital to a system.
Related tools: solar and storage calculator, electricity cost calculator, live electricity prices, astronomical clock.