Some major UK cities and their solar power potential (Produced by Chris Nankervis, August 2006)
*Factors considered for this chart include; (1) Day Length (2) Solar Zenith / Latitude (3) Statistics of sunlight hours (4) 15% efficiency of panels (5) panels orientated in solar zenithal and azithmal plane. Data Column 1; Index (fraction of Exeter Solar Power), Data Column 2; Number of energy saving lightbulbs a 1mx1m panel would power in an average year, Data Column 3; Power output for 9 x (1mx2m) panels (mean), Data columns 4-6; KWh per day.
*The above figures are an approximation to the output expected from your solar panels. A typical family household (e.g. a 3/4 bedroomed detached property) can expect around 40-50% of their energy consumption to be provided by photovoltic cells on the roof, though it is greatly variable and the majority of power is generated during the summer months during clear conditions. The west counties and the far SW are by far the best locations for solar panels. Regional and positional variations affect the output, as does the efficiency of your panels. Rural regions, especially at higher altitudes and to the lee of mountains can experience more output associated with cleaner air and clearer skies. A solar panel should be installed in the correct position in order to be most efficient at harnessing the sun's energy. The panels should be as close to south facing as possible and in the mean sun hemispheric plane. Most panels have a maximum output (usually around 160W per panel), this means that the panel should be orientated towards a mid-late Spring zenith angle. As a rough estimate {90 degrees - ((2/pi)*latitude + 7.8 degrees)} should give a relaistic zenith angle. Around 60 zenith is typical for the UK (steeper than the modern day roof. Obtain planning permission before installing any panels - often laws are quite strict in the UK.