Solar panels: 3–5 sun-hours a day

1 kW of panels yields roughly 3–5 kWh per day in temperate climates, averaged over the year.

Why it works

"Peak sun hours" bundle up weather, season and sun angle. Deserts push toward 6; cloudy northern winters can dip below 1.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

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More in Environmental

• Lightning distanceCount the seconds from flash to thunder, divide by 3 for kilometres (by 5 for miles).
• Air cools as you climbTemperature drops about 6.5 °C for every 1,000 m of altitude.
• Pressure halves every ~5.5 kmAtmospheric pressure falls by half roughly every 5,500 m you climb.
• Ten metres of water = one atmosphereEvery 10 m of seawater adds about 1 atmosphere of pressure.

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