Solar Electricity (PV): The Basics
Solar PV systems use solar panels attached to your roof, wall or freestanding in your garden to capture the sun's energy and convert it to electricity for use in your home. The photovoltaic cells that make up the solar panels contain a semiconductor material such as silicon, which when exposed to light energy converts this energy into electricity.
An average household installing a solar PV system could save around £140 a year in electricity bills. You could also receive payment for the electricity you generate using solar PV from the government's Feed-in Tariff (FIT) Scheme. Here's how it works:
- Your energy supplier pays you a 'Generation Tariff' for every unit of electricity you generate whether you use it or not, at a rate set from when you apply for payment. You are then paid every year for 20 years. At current tariff rates of 15.44p/kWh an average home could be paid £370 a year.
- Any electricity you generate is free to use. If you need more electricity than your system is generating at any point you can import some electricity from the grid as you do now, which you will pay for. However, overall you will still make a saving on your electricity bill.
- Any excess electricity that is generated over and above what you use can be sold back to the Grid. This is called the 'Export tariff' and is set at 4.5p/kWh. Export commonly happens when you are out and using minimal electricity. This can earn an average household approximately £50 per year.
How solar PV systems work
- The solar panels and tiles used in solar PV systems are made up of multiple photovoltaic cells. These cells contain layers of a semiconductor, usually silicon, covered by a layer of non-reflective glass.
- These panels can be mounted on the roof of a house either directly or on a frame, on an outside wall or freestanding on the ground outside your house. They are available either in the conventional panel format or as solar tiles which can be used in place of standard roof tiles in your roof. They are more expensive than solar panels and can be less efficient, and so should only be considered if aesthetics are a strong consideration or your local planning restrictions prohibit standard panels.
- When the PV cells are exposed to sunlight, the semiconductor layers absorb some of the light energy, generating an electric field across the layers. This is Direct Current (DC) electrical energy.
- This electricity is collected into a central part of the roof system behind the panels.
- The system then uses an inverter to convert the DC electricity to Alternate Current (AC) electricity for use in your home.
- Any surplus electricity is fed automatically into the grid, and similarly if you need to use electricity from the grid this is supplied automatically.
The amount of electricity you export is not currently measured but assumed to be about 75% of the electricity you generate. The photovoltaic cells are capable of working in any level of sunshine so will continue to produce electricity in cloudy conditions. The ability of a solar PV system to generate electricity does vary from system to system and is described using the term kilowatts peak (kWp), which is the system's level of peak performance. This can range from approximately 0 to 4. The average capacity of a domestic system is 3kWp.
Installing solar PV systems
For your home to be suitable for a solar electricity installation you will need to have free access to your roof. This means that you either own freehold of the property, or that if you have leasehold or are renting you can get permission from whoever owns the property. For the same reason non-top floor flats are not suitable for this type of installation. You will also need to have a metered electricity supply.
Solar PV Installation Checklist:
You should take the following factors into consideration:
- Panel format: Solar PV cells are available in a number of formats, including solar panels directly installed onto a roof or wall, solar panels on a frame on a roof or freestanding and solar tiles. Using a frame for solar panels allows you to change the angle of incidence of the installation to maximise the panels' sun exposure.
- Location: Ideally your solar panels or tiles should be in a south facing location at a 30 degree angle of incidence, but any south east or south west facing location is feasible. It's important that the location isn't shaded between 10am and 4pm at the very least.
- Roof integrity: It's a good idea to check with your installer that your roof is capable of bearing the weight of your panels as they may be heavy.
- Roof space and shape: This will depend on the size of your southerly facing roof or surface. An average installation will take up around 6-20 square metres on your roof. Each solar panel measures around 1.5 square metres, making the system flexible enough to fit most roof shapes.
- Planning permission: You should not normally need planning permission to install a solar PV system. There are permitted development rights for solar PV systems unless the solar panels are more than 20cm tall when on the roof.
- Your insurance: The majority of insurance companies cover solar electricity installations but it is still a good idea to check exactly what your insurer covers before you have the system installed, as well as checking how the installation will affect your insurance package.
- Your energy supplier: Larger energy companies are legally obliged to be FIT suppliers but smaller companies are not. It's a good idea to check with your energy supplier to see what they offer.
Solar PV Costs
According to the The Energy Saving Trust an average solar PV system of 3kWp will cost around £4000-£5000 including 5% VAT, although quotes will vary significantly from installer to installer as the cost of solar PV systems has fallen dramatically in recent years meaning that there are now 4 kWp systems available for less than £5,000. There are some general rules as to how much you will pay:
- Solar tile systems are generally more expensive than solar panels but can be used to repair your roof should any tiles need replacing. This would offset the cost of the installation.
- The larger the kWp of a system the more expensive it will be but the more the system will save you on your energy bills. The extra money you pay for each added unit of kWp also decreases with increasing value, making higher kWp systems better value for money, however if you exceed 4 kWp the Feed -In Tariff drops to 14.5p from 16p/kWh.
From the date you register to receive FIT payments you will be paid a generation tariff for every unit of electricity you generate, and an export tariff for every unit you export, with an average system making around £420 a year. For more information on the FIT scheme, visit our Feed-in Tariff (FIT) guide .
The average payback time for a solar PV system is around 10 years, but beyond that time you will make money. An average installation can make around £5000 more than the cost of all installation and maintenance over its lifetime of 25 years.
Running a solar PV system requires little maintenance. You will need to make sure that trees do not shade out the panels and keep the panels free of any debris, particularly in the case of ground based panels. If the panels are roof mounted at an angle the rain should keep the panels clean. If you do need to clean your panels, you can do so by cleaning them as you would windows - with water and soap using a ladder or a high pressure washer. Many window cleaning specialists offer a solar panel cleaning service.
Your installer will give you information on signs to look out for to spot any problems with the system. The system will last around 25 years and as such is guaranteed for that time, but during this time your inverter will probably need to be replaced at a cost of about £1,000.
The installation time for a solar PV system will vary with the size of the system you wish to install and various other factors such as any requirement for scaffolding, however 1 day is given as a guide installation time for a sub 4 kWp domestic system.
Solar PV Installers:
To qualify for FIT payments you will need to get an MCS accredited installer to carry out your installation using MCS accredited products. Your installer will then give you an MCS certificate that you will need when applying for FIT payment. For further information on the FIT scheme, visit our Feed-in Tariff page.
The benefits of solar PV systems
The average home would make a saving of around £560 a year after installing a solar electricity system. This includes the saving you would make on your electricity bill and the FIT payment you would receive from your energy supplier. More information on the FIT scheme is available on our Feed-in Tariff page. Solar PV systems also deliver other benefits:
- Reduce your carbon footprint: An average solar PV system will save around 20 tonnes of CO 2 over its lifetime.
- Very little maintenance: After the installation is complete you can maintain the system with little expenditure and effort.
- Year round free electricity: Your solar PV system will continue to work through the winter months.
Solar PV - maximising your savings:
You can maximise the savings that a solar PV system will give you on your electricity bills by trying to run your energy hungry appliances during the day when the panels are generating, rather than at night when they are not. If you are frequently out during the day, you can buy appliances with a timer feature so that they come on after you have left.