Lots of people in the UK worry that cloudy skies will stop solar working. The good news is panels use daylight, not direct sun. Daylight gets through clouds just fine.
How much power do you lose in cloud?
On a heavily overcast day, a panel makes about 10 to 25 percent of its sunny-day output. Light or hazy cloud cuts output far less than that. That's a dip, not a shutdown. Your roof still makes power whenever it's bright enough to read outside.
Why do yearly totals matter more than one day?
Installers size a system around a whole year of weather, cloudy days included. Germany gets less sun than the UK, yet it runs more solar than almost anywhere. That's because the maths already accounts for clouds.
Sunny says
If your area is especially dull, the fix is usually a bigger array or a battery, not skipping solar altogether. A slightly larger system covers the grey days too.
The quick version
- Panels still make 10–25% of output on a heavy overcast day.
- Year-round totals matter more than any single cloudy day.
- Even cloudy UK regions can make solar pay.