Solar PV (photovoltaic) panels generate electricity from the sun's energy that can be used to run domestic appliances. They generate electricity without burning fossil fuels, such as coal, oil or gas and help to limit greenhouse gas emissions. This supports the national and international commitments to reduce greenhouse gas emissions and provides a portion of your electricity for free. 

The output of the system depends upon its orientation, size and available sunlight. A system is rated on its peak output, reffered to as kilo-Watt-peak (kWp). This is the peak output power (in kW) under full sunlight conditions. The Energy Saving Trust estimates that a 2kWp-sized system can save you up to £200 on your electricity bill and provide 40% of your electricity needs a year.

You can use PV systems on any  building with a roof that faces between south east and south west, as long as no other buildings or large trees overshadow it. PV arrays can also be mounted on the ground if required. Less energy will be generated if the roof surface is in shadow for parts of the day, but it will still generate some electricity. Output varies with season and the time of day. It is highest during summer months on sunny afternoons.

The graph below shows the projected output per month for a 1.38kWp system on a Southwest facing roof in Cumbria.

 How does it work?

Sunlight is absorbed by the roof mounted panel creating a flow of electricity. This is fed into the inverter which converts the electricity to a form which can be either used in the building or fed back to the supply grid via the existing distribution board.

The actual amount of electricity produced by the PV system is shown on the energy meter and optional remote display (shown below). The remote display can also be configured to show the total amount of energy prodiced and the CO2 emmissions saved.

Most domestic installations are under 4kWp output. Systems above this size require special certification for the Electricity Company (Distribution Network Operator), which may incurr additional costs.