Since the majority of electricity in commercial buildings is used between the hours of 9am and 5pm there is an excellent correlation between the electricity supplied by a solar facade and the building’s overall demand for electricity. As a result, eighty to ninety per cent of the electricity generated by solar photovoltaics can be used directly within a building to power computers, lights etc 9.

Solar buildings in Europe are usually connected to the electricity grid to allow any surplus electricity generated by photovoltaics to be exported for use by other consumers. Grid connection also means that electricity can be imported when necessary, to meet additional electricity needs which cannot be met by solar photovoltaics. Maximising the energy efficiency of a commercial building will increase the proportion of electricity that can be provided by solar photovoltaics.

The percentage of a commercial building’s electricity demand which can be met by solar photovoltaics obviously varies according to the amount installed and the time of year. However, over the course of a year, a typical solar photovoltaic installation could generate roughly thirty per cent of the annual electricity requirements of a commercial building.

In the UK it is possible to generate 75 units of electricity per year from each installed square metre of solar facade vertically deployed in a due south orientation and assuming no shading10. Electricity output increases to around 100kWh per square metre if the solar application is tilted at the optimum 30° tilt angle. A vertical solar facade orientated in a due west or due east direction would generate around fifty per cent of the output of a facade facing due south.