Solar insolation map of the UK

The map shows the amount of energy, in kilowatt hours (kWh - the unit that mains electricity is sold in), that a 1 kW array of solar panels angled at the optimum angle will generate over an average year in the UK.

Further north, the sun is a little lower in the sky, which means that it takes a longer path through the atmosphere so that less energy reaches the ground. So, if you're a Shetlander - sorry, you're going to get less energy than average from your solar array - around 750 kWh per kW per year. If you're from sunny Cornwall, however, you're in luck - you should be able to generate approx 1000 kWh per kW per year!

Cloudiness also makes a difference, so the east coast of Scotland is a little better than the west coast.