Solar PV (photovoltaic) uses energy from the sun to create electricity to run appliances and lighting. PV requires only daylight, not direct sunlight to generate electricity and so can still generate some power on a cloudy day.
In this article
How does it work?
Photovoltaic systems use cells to convert sunlight into electricity. The PV cell consists of one or two layers of a semi conducting material, usually silicon. When light shines on the cell it creates an electric field across the layers causing electricity to flow. The greater the intensity of the light, the greater the flow of electricity.
PV cells are referred to in terms of the amount of energy they generate in full sunlight, know as kilowatt peak or kWp.
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The benefits
PV systems produce no greenhouse gases and each kWp can save approximately 455kg of carbon dioxide emissions per year, adding up to about 11 tonnes over a system's lifetime.
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Is it suitable for my home?
You can use PV systems for a building with a roof or wall that faces within 90 degrees of south, as long as no other buildings or large trees overshadow it. If the roof surface is in shadow for parts of the day, the output of the system decreases.
PV arrays now come in a variety of shapes and colours, ranging from grey 'solar tiles' that look like roof tiles to panels and transparent cells that you can use on conservatories and glass to provide shading as well as generating electricity.
Solar panels are not light and the roof must be strong enough to take their weight, especially if the panel is placed on top of existing tiles.
Some local authorities require planning permission to allow you to fit a PV system, especially in conservation areas or on listed buildings. Always check with your local authority about planning issues before you have a system installed. Obtaining retrospective planning permission can be difficult and costly.
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Costs and savings
Prices for PV systems vary depending on the size of the system to be installed, type of cell used and the nature of the actual building on which it is mounted. The size of the system is dictated by the amount of electricity required.
For the average domestic system, costs can be around £5000–8000 per kWp installed with most domestic systems usually between 1.5 and 3 kWp. Solar tiles cost more than conventional panels and panels that are integrated into a roof are more expensive than those that sit on top.
If you intend to have major roof repairs carried out it may be worth exploring PV tiles as they can offset the cost of roof tiles.
You could be saving up to 1.1 tonnes of CO2 a year and this could mean £150–200 off your electricity bill*.
Grid connected systems require very little maintenance, generally limited to ensuring that the panels are kept relatively clean and that shade from trees has not become a problem. The wiring and components of the system should however be checked regularly by a qualified technician.
Stand-alone systems, i.e. those not connected to the grid, need maintenance on other system components, such as batteries.
*Savings are dependent on the level of on-site consumption and/or value of export tariff. Assumes a 2.5kWp system with 50 per cent - 100 per cent on-site consumption with excess exported to grid on a typical export tariff.
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Where can I find out about installation?
The BERR funded low carbon buildings programme provides grants to help with the costs of installing solar PV technologies. To be eligible for a grant you will need to use a certified installer and products.