Słonecznik PV (“Sunflower PV”): how much power will your solar panels make tomorrow, next week and over the whole year?
I built a free web app for owners of solar PV systems. It answers one question: how many kWh will my panels produce today, over the next 7, 14 or 16 days, and across the next 12 months?
🔧 What it’s for
Planning consumption: when to run the washing machine, dishwasher or heat pump, or charge the car. An hourly map highlights the 3 best hours of every day. Deciding on home batteries and self-consumption. Checking that your system works properly by comparing the forecast with the real yield from your inverter. Putting a value on your energy using live hourly market prices (Polish net-billing).
⚙️ How it works
Weather forecasts from 6 models at once (ECMWF, GFS, ICON, Météo-France, UK Met Office, ECMWF AIFS), combined into one consensus with an honest uncertainty range. Radiation converted hour by hour into the output of your panels. It accounts for kWp, tilt, azimuth, two roof planes, panel temperature, losses, inverter limit, soiling, snow, degradation, monthly tree shading and the terrain horizon. The 12-month outlook is a simulation over 8 years of ERA5 historical data with a P10–P90 range, so you see a weaker and a better year, not just the average. It learns from your data. Enter yields or upload screenshots from your inverter app, and the forecast adapts to your roof. A backtest shows how accurate the forecasts have been at your location.
🔌 Data sources and integrations Open-Meteo (forecasts, ERA5, satellite data, CAMS dust, terrain model), IMGW (Polish weather stations and warnings), PSE (live RCE prices), OpenStreetMap (address search), Huawei FusionSolar via Kiosk link (live power every 5 minutes) and Home Assistant (also available as an HA add-on).
🔒 No account, ads, cookies or analytics. All your data stays in your browser. 📱 Works on desktop and mobile, free to use, available in English and Polish.
