Solar Output Calculator

Summer vs winter solar estimator

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Tap the map to move the pin, or press "Use my location".

i Estimates. Download OnSun to predict your solar

Assumes an unshaded roof and a 90% system performance ratio. Sunny curves are clear-sky physics for the solstices at 5-minute resolution; the cloudy view is a simulated broken-overcast day; the annual figure applies a typical-climate adjustment for your latitude. Curves are drawn in local solar time. Because the sunny curves are clear-sky, the summer-vs-winter ratio shown here excludes winter's extra cloudiness; real seasonal gaps are usually larger. Your local weather can move the annual number 20% either way.

Results are estimates for a typical weather year, not advice and not a quote. Terms of Use · Privacy

What the numbers mean

The two curves are the solstices: your longest solar day and your shortest, drawn in local solar time. The gap between them is set almost entirely by your latitude, which is why a winter day at a third of your summer peak is normal in London and would be worth investigating in Brisbane. Flip the cloudy switch to see how much a heavily overcast sky takes off, and drag the tilt slider to see which way the seasonal trade-off goes for your roof.

Read the long version in solar panel output: summer vs winter and cloudy days, or see where the savings actually come from in feed-in tariffs vs self-consumption and is a home battery worth it.

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