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Solar panel angle in winter and summer

A fixed panel at the best year-round angle loses surprisingly little. Adjusting it twice a year gains about five per cent under clear skies, and adjusting it every month six to seven. Here are the angles and the gains for seven latitudes, from the site’s clear-sky model.

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The baseline

The best fixed angle

A panel collects most when the sun shines straight onto it. Because the sun is higher in summer than in winter, no fixed angle is right all year; the best compromise tilts the panel a little less steeply than the latitude.

Best tilt for a panel facing the equator, clear sky, 2026
LatitudeWhole yearApril–SeptemberOctober–MarchGain, two seasonsGain, monthlyFlat panel
30°28°8°49°+5.7%+7.0%−10.0%
35°32°13°54°+5.5%+6.9%−13.3%
40°37°18°58°+5.3%+6.7%−16.9%
45°41°23°62°+5.1%+6.5%−20.6%
50°44°28°66°+4.8%+6.1%−24.3%
55°47°33°70°+4.3%+5.7%−27.6%
60°50°38°73°+3.7%+5.1%−30.2%

The gains compare the yearly energy against a panel fixed at the year-round optimum. Turning the panel twice a year, at the equinoxes, between the summer and the winter angle gives four to six per cent more; the summer angle is about 20° flatter than the year-round one and the winter angle about 20° steeper.

Month by month

The ideal angle each month

Best tilt each month, clear sky
LatitudeJanFebMarAprMayJunJulAugSepOctNovDec
40° N66°57°44°28°13°5°9°21°37°53°64°68°
50° N74°66°54°38°22°15°19°31°47°62°72°76°

The ideal angle swings by about 60° over the year. At midsummer a nearly flat panel catches the high sun best; in December one tilted at 70° or more, almost a wall, does. Adjusting every month is worth only a percent or two more than adjusting twice a year.

A common question

What does a flat panel lose?

A panel lying flat loses 10% of the clear-sky yearly energy at 30° latitude and over 30% at 60°, mostly in winter, when the low sun hits it at a grazing angle. Flat panels also collect dirt and snow. Real installations on flat roofs are usually tilted 10 to 15° for that reason, often facing east and west in rows to fit more panels on the roof.

The decision

Is adjusting worth it?

  • Roof-mounted systems: no. The gain is a few per cent, and climbing onto a roof twice a year costs more than it earns. Set the year-round angle, or simply follow the roof.
  • Ground mounts and garden arrays with an easy adjustment: twice a year is a cheap gain, and the winter angle also sheds snow.
  • Off-grid cabins used in winter: choose the winter angle, roughly the latitude plus 15°, and leave it there. The panel produces less in summer, when there is energy to spare, and the most when it is scarce.

Limits of the numbers

Clouds change the answer

The figures come from a clear-sky model: the sun’s position every 15 minutes through the year, the direct and diffuse sunlight a cloudless sky delivers, and the angle at which each reaches the panel. Clouds change two things. They cut the direct beam, which matters more for a steep winter panel, and they add diffuse light from the whole sky, which a flatter panel sees more of. In a cloudy climate the best year-round angle is therefore a few degrees flatter than in the table. For a contract, use measured climate data, such as the European Commission’s PVGIS.

The solar panel angle calculator runs the same model for your exact location and orientation, and shows the energy month by month. To see where the angle comes from, read about the sun’s elevation through the year.

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