Solar electricity systems capture the sun's energy using photovoltaic (PV) cells. The cells convert the sunlight into electricity, which can be used to run household appliances and lighting. PV cells don't need direct sunlight to work - you can still generate some electricity on a cloudy day.

PV cells are panels mounted to an unshaded roof or wall facing south (or near south). Each cell is made from one or two layers of semi conductingmaterial, usually silicon. When light shines on the cell it creates an electric field across the layers. The stronger the sunshine, the more electricity is produced.

The output from the PV panels is matched with your household's electricity supply by an inverter. The inverter ensures that its output voltage is slightly higher than that coming in from the grid, which means your appliances will use the electricity from your PV system before they start drawing from the grid, thus reducing your energy consumption. If your PV system is generating more than is required by your appliances at any given moment, the surplus energy you generate will be exported onto the grid.

Because the output varies with external light conditions, the referenced output from a PV system is always the yield achieved over a full calendar year,rather than its capacity to drive a particular appliance at any given point in time. The strength of a PV cell is measured in kilowatt peak (kWp) - that's the amount of energy the cell generates in full sunlight.