Solar power is a renewable and practically inexhaustible energy source. However, the proportion of this energy that can be harnessed to generate electricity is limited by current technology and the UK's climate.
It is thought that in practice, taking various limitations into account, the UK could potentially generate a maximum of 140 billion kilowatt-hours per year (kWh/year) from solar power. In 2009, the UK's total demand for electricity was around 379 billion kWh.
The UK lies at a relatively high latitude, where it is generally less sunny and the sun is not as high in the sky as it is near the equator. London receives 0.11 kilowatts of sunshine per square metre (kW/m2) on average, compared with 0.19kW/m2 for Athens, which is nearer the equator, and 0.24kW/m2 for Cairo, which is nearer still.
Solar panel efficiency
A solar panel's conversion efficiency is the proportion of the solar energy striking the panel that it can convert into electricity. The solar panels found most commonly on UK homes are photovoltaic (PV) cells, which typically have a conversion efficiency of 10%.
This means that, to meet the UK's average peak electricity demand of 60 million kilowatts (kW) using solar power alone, an area nearly 30 times the size of Greater London would need to be covered with solar panels. Even such a vast, impractical PV installation as this would require backup from other energy sources at night, during winter and on cloudy days.
These are the quantity of supply challenges facing solar power. Read about the possible solutions.