How much energy is there in sunlight?

It's interesting to calculate (or measure) the amount of energy in sunlight - and to work out how much energy one might get.

Let's think about photovoltaic panels. These are the ones which you see at the side of the road near speed cameras and other traffic-controlling devices.

The price of these has come down quite a lot in the last 20 years but the efficiency is more or less the same - 10% and you're doing well.

Right- let's take a square metre of ground. These are the approximate figures I use for solar panel calculations; they refer to midday:

1000 Watts - Death Valley, or African desert on a hot day
600 watts - hottest day you'll ever get in the UK
500 watts - hot summer day
200 watts - hot summer day with light cloud cover
100 watts - sunny, clear day in December
50 watts - overcast day in December

Divide the figures by 10 and you'll get a slight over- estimate of the power from your metre-square photovoltaic panel.

It's a sobering thought that most solar panels are net consumers of energy. A panel which generates as much energy (over its lifetime) as it took to make it in the first place is doing well.

Back to top

Energy Policy
Fuel to Electricity
Nuclear Power
Wind Turbines