What can your roof really produce?
Find your house, trace each roof face on the satellite photo and see the yield, how much of it you would use yourself, and when it pays back. Calculated hour by hour from three years of satellite sun data, with your heat pump, car and battery.
- ✓ No sign-up, no email
- ✓ Nothing stored on a server
- ✓ Hourly simulation, not rules of thumb
How the calculation works
Your roof, measured on the photo
Each face you draw is measured from the satellite image and enlarged by its pitch, because the photo shows the roof from above. 70 % of the sloped area is counted as usable for 440 Wp modules; edges, ridge, chimneys and windows take the rest. You can override the panel count.
Sun data for that exact spot
Every face is sent with its pitch and direction to PVGIS, the EU Joint Research Centre's solar database. It returns hourly output for 2021–2023 from satellite measurements, including shading by hills and mountains on the horizon. Trees and neighbouring buildings are not included.
Your consumption, hour by hour
Household use follows a standard household profile: more in the evening and in winter. A heat pump follows the outdoor temperature at your location, with a COP that falls in the cold. An electric car charges either in the evening or on solar surplus.
Battery and money
For all 8760 hours of the year, solar power first covers consumption, then charges the battery, and the rest goes to the grid. Payback counts 0.5 % module ageing per year, 2 % rising electricity prices and 1 % of the investment per year for upkeep.
Why another solar calculator?
- Google’s Project Sunroof analyses roofs automatically, but only in a few countries, mainly the US.
- PVGIS has the best open sun data for Europe, but you must know your pitch and direction, and it stops at production: no self-consumption, battery or heat pump.
- Most installer calculators want your phone number first and hide their assumptions.
- This one shows every assumption, lets you change the prices, and compares battery sizes side by side.
Questions
- How accurate is the result?
- The sun data is good to a few percent for an unshaded roof. The biggest uncertainties are shading by trees and neighbours, and your real consumption pattern. Treat the result as a solid estimate for planning, not as a yield guarantee.
- How do I find my roof pitch?
- Typical pitches are 30–45° for tiled roofs, 15–25° for bungalows and below 10° for flat roofs. Plans, the roofer or a phone inclinometer app on a window in the attic give the exact value.
- Does a battery pay off?
- It depends on how much surplus you have in the evening. The table under the result compares no battery with 5, 10 and 15 kWh using your own numbers, so you can see whether the higher self-sufficiency is worth the price.
- Which prices are preset?
- Typical Austrian prices in late 2026: 0.26 €/kWh for grid electricity including fees, 0.06 €/kWh feed-in, 1,300 €/kWp for an installed system and 500 €/kWh for a battery. Change them to your offer.
- Is my address stored?
- No. The address search and the sun data are fetched by this site’s server without storing anything, and your roof lives only in the link of this page. Share the link and the other person sees the same calculation.
Sun data: PVGIS © European Union, 2001–2026. Address search: Photon, © OpenStreetMap contributors. Imagery: Esri, Maxar, Earthstar Geographics.