The average domestic solar PV system is 4kW and on average costs between £4,500.00 and £6,000.00 (including VAT at 5%). Costs have fallen significantly over the last year. They vary between installers and products, so we recommend getting quotes from at least three installers.

Other 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. Further information on Green Deal.

A 4kW system can generate around 3,700 kilowatt hours of electricity a year – roughly equivalent to a typical household's electricity needs. It will save nearly two tonnes of carbon dioxide every year.

If your system is eligible for the Feed-In Tariff scheme it could generate savings and income of around £770.00 a year if you register before 31st March 2014 (based on a 4kWp solar PV system eligible for a generation tariff of 13.52p/kWh). You will get paid for both the electricity you generate and use, and what you don't use and export to the grid. Find out more about how we made these calculations.

When applying for the Feed-In Tariff scheme, you will need to show evidence of your property's Energy Performance Certificate and this will affect what tariff you can get. If you know your system size, you can get a tailored estimate for your system using our Solar Energy Calculator. Please note that the Feed-in Tariff scheme is not available in Northern Ireland.

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 soapy warm water 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. 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.