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Solar Panels

Generate cheap, green electricity from sunlight

Solar panel electricity systems, also known as solar photovoltaics (PV), capture the sun’s energy using photovoltaic cells. These cells don’t need direct sunlight to work – they can still generate some electricity on a cloudy day. The cells convert the sunlight into electricity, which can be used to run household appliances and lighting.

The benefits of solar electricity 

  • Cut your electricity bills: sunlight is free, so once you’ve paid for the initial installation your electricity costs will be reduced.
  • Get paid for the electricity you generate: the government’s Feed-In Tariffs pay you for the electricity you generate, even if you use it.
  • Sell electricity back to the grid: if your system is producing more electricity than you need, or when you can’t use it, you can sell the surplus back to the grid.
  • Cut your carbon footprint: solar electricity is green, renewables energy and doesn’t release any harmful carbon dioxide] or other pollutants. A typical home solar PV system could save over a tonne of carbon dioxide per year – that’s more than 30 tonnes over its lifetime.

How do solar panels (PV) cells work? 

PV cells are made from layers of semi-conducting material, 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. Groups of cells are mounted together in panels or modules that can be mounted on your roof.

The power of a PV cell is measured in kilowatts peak (kWp). That’s the rate at which it generates energy at peak performance in full direct sunlight during the summer. PV cells come in a variety of shapes and sizes. Most PV systems are made up of panels that fit on top of an existing roof, but you can also fit solar tiles.

Solar tiles and slates

Solar tiles are designed to be used in place of ordinary roof tiles. A system made up of solar tiles will typically cost around twice as much as an equivalent panel system, although you will save the money you would have spent on roof tiles or slates. Solar tile systems are not normally as cost-effective as panel systems, and are usually only considered where panels are not considered appropriate for aesthetic or planning reasons.

Solar Power Explained

solar diagram

Costs, savings and maintenance

Costs

Factors that affect PV installation costs are:

  • The more electricity the system can generate, the more it costs but the more it could save.
  • Larger systems are usually more cost-effective than smaller systems (up to 4kWp).
  • PV panels are all around the same price per kWp, but PV tiles cost much more than a typical system made up of panels.
  • Panels built into a roof are more expensive than those that sit on top.

Green Deal finance and renewables

This technology is an eligible measure under the UK government’s Green Deal which is a financing mechanism that lets people pay for energy-efficiency improvements through savings on their energy bills.

Savings

A 3.5kWp system can generate around 3,000 kilowatt hours of electricity a year – about three quarters of a typical household’s electricity needs. It will save over a tonne of carbon dioxide every year.

If your system is eligible for the Feed-In Tariff scheme it could generate savings and income of around £645 a year (based on a 3.5kWp solar PV system eligible for a generation tariff of 15.44p/kWh). You will get paid for both the electricity you generate and use, and what you don’t use and export to the grid. When applying for FITs you will need to show evidence of your property’s Energy Performance Certificate and this will affect what tariff you can get.

Maintenance

Solar PV needs little maintenance – you’ll just need to keep the panels relatively clean and make sure trees don’t begin to overshadow them. In the UK panels that are tilted at 15° or more have the additional benefit of being cleaned by rainfall to ensure optimal performance. Debris is more likely to accumulate if you have ground mounted panels.

If dust, debris, snow or bird droppings are a problem they should be removed with warm water (and perhaps some washing-up liquid or something similar – your installer can advise) and a brush or a high pressure hose (or telescopic cleaning pole) if the panels are difficult to reach. Always be careful if you are working above the ground or near the top of a ladder. Alternatively, there are a number of specialist window cleaning companies who will clean solar PV panels for you at a cost (of around £30 based on our research in March 2012) depending on the size of your array and location. Many of these companies use a water fed pole system which does away with the need for a ladder.

Once fitted, your installer should leave written details of any maintenance checks that you should carry out from time to time to ensure everything is working properly. This should include details of the main inverter fault signals and key trouble-shooting guidance. Ideally your installer should demonstrate this to you at the point of handover. Keeping a close eye on your system and the amount of electricity it’s generating (alongside the weather conditions) will familiarise you with what to expect and alert you to when something might be wrong.

The panels should last 25 years or more, but the inverter is likely to need replacing some time during this period, at a current cost of around £1,000. Consult with your installer for exact maintenance requirements before you commit to installing a solar PV system.