According to Oxford Brookes University the average UK household with a south facing roof receives about 1000 KWh/m2 (Kilowatt/Hours per metre square) of solar energy per year. If you have been up in the attic of a house on a summersí day one will have felt the direct effect of that energy, it gets pretty hot up there!
The chart above illustrates the average exposure on a 30 degree south facing roof. Depending on the latitude of the house the energy saving contribution to hot water and space heating is from 30% to 70%. The higher values are for the south of the UK. Effectively any solar panel should give at least a total hot water demand in the summer months.
Given the average gas utility bills from Energywatch the contribution saved can be calculated.
Source: Solar Trade Association.
UK Annual Irradiation Total Kwh/m2.
For instance. £1100 per year for gas including VAT for cooking, hot water and central heating for a house in the midlands UK.
£1100 x 97% (hot water & central heating contribution, 3% cooking deducted) x 55% (energy saving) = £586.85 pa.
The above figures may not sound that impressive but it is the household insurance premium saved each year. For companies heating large storage areas and families not intending to move in the mid-term the savings are very substantial and can be seen from installation.