How to use this tool
- Set your location. The best angle depends mainly on latitude.
- Enter your roof. Set the tilt (0° is flat, 90° vertical) and the direction the panels face. The chips set the main compass directions.
- Read the result. The first card shows what share of the best possible yearly sunlight your roof gets in typical weather. Next to it are the best fixed tilt and direction, and the best tilts for summer and winter.
- Compare options. The monthly chart compares your roof with the best orientation, and the table shows the percentage for every combination of tilt and direction.
How it is calculated
The tool simulates the sun over a full year: every 15 minutes on every fourth day, it calculates the sun’s position. For each month it takes the share of sunlight that typically gets through the clouds at your latitude, splits it into direct light from the sun and diffuse light from the sky, and adds a little light reflected from the ground. It adds up what falls on a panel with your tilt and direction, then tries every tilt from 0° to 90° to find the best. Full details are on the methodology page.
Because cloudy days are included, the results come within a few percent of the PVGIS rules of thumb: in Berlin, for example, the best tilt is about 38° and a flat panel gets about 86% of the best. The weather is a smooth average for the latitude, not local records, so a sunny valley or a foggy coast can differ. The relative comparison between orientations is the most reliable part.
Rules of thumb
- Face the equator: south in the Northern Hemisphere, north in the Southern.
- Within about ±15° of the best tilt and ±30° of due south, the loss is usually under 5%.
- The flatter the panel, the less its direction matters.
- East-west layouts produce less in total but spread production across the day.
The guide best tilt and orientation for solar panels explains the trade-offs, and the sun path over my house tool shows which roof side gets the most sun.
Last updated September 23, 2026