Solar electricity panels, also known as photovoltaics (PV), capture the sun’s energy and convert it into electricity that you can use in your home. By installing solar panels you can generate your own renewable electricity.
If you're thinking of getting solar panels installed on your property, its best to get some impartial advice first, and find out exactly how it all works. This article is from the Energy Saving Trust - a national service for impartial advice on energy related topics.
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How do solar PV cells work?
Solar PV cells are made from layers of semi-conducting material, usually silicon. When light shines on the material, electrons are knocked loose, creating a flow of electricity. The cells don’t need direct sunlight to work, they can work on a cloudy day. However, the stronger the sunshine, the more electricity generated. Solar PV cells are grouped into modules, and modules are usually grouped into solar arrays. Modules and arrays come in a variety of shapes and sizes.
Most PV systems are made up of panels that fit on top of your roof, but you can also install on the ground, or fit solar tiles.
The electricity generated is direct current (DC), whereas the electricity you use for household appliances is alternating current (AC). An inverter is installed along with the system to convert DC electricity to AC.
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 about twice as much as an equivalent panel system.
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.
Are solar panels right for you?
Do you have enough space?
Space is a key consideration. As a general guide, a roof area of 10-20 square metres would be enough to deliver between 20% and 45% of the typical household’s electricity needs. This roof space will ideally face South, will be unshaded, and at a pitch angle of about 30 or 40 degrees.
East- or West-facing roofs could still be considered, but North-facing roofs are not recommended.
Any nearby buildings, trees or chimneys could shade your roof and have a negative impact on the performance of your system.
Do you need planning permission?
Solar PV installations are classed as permitted developments, but always check with your local authority before installing in case there are any limits or restrictions applicable.
You can find out more about choosing a site and getting planning permission.
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Getting the most out of your solar PV system
Reduce your electricity use
During daylight hours, you’ll be generating electricity even on cloudy days, but during the evening you’ll be using electricity from the mains. Reducing your electricity use can help lower your bills and reduce your carbon footprint. Remember to turn devices off and avoid standby, and see our energy saving quick wins for more tips to reduce your energy use.
Use more electricity during the day
As your PV system will be working at its peak during daylight hours, it’s a good idea to think about reorganising domestic activities such as washing, dishwashing and ironing. If you’re home most of the day, then this will be easier to do, but if you work during the day then try setting up timers for your dishwasher and washing machine.
Insulate your home
If you have electric heating, programming your timers to come on during daylight hours will help you save money on your electricity bills. To keep that heat in your home for longer, insulate your roof or loft, and add insulation to your cavity wall or solid wall. Draught-proof your doors and windows as well to prevent draughts.
Combine with other renewable systems
You can combine PV with other space-heating renewable technologies such as heat pumps, solar thermal systems and wind turbines. These technologies work well with each other, as PV can be set up to help power a heat pump, for example, or several of these systems can feed into a thermal store.
Install a PV diverter
Most of the time your solar PV system either:
isn’t generating enough energy for your household’s demand, and is supplemented by importing electricity from the grid, or
is generating excess electricity surplus to your demand, and exporting that electricity back to the grid.
If you are getting export payments via Smart Export Guarantee or if you aren’t getting paid for exports at all, you might be looking for a way to use more of your generated energy within your home.
Instead of sending it to the grid, that surplus electricity could power the immersion heater in your hot water tank, storing hot water for you to use later.
A PV diverter would allow you to do this, provided you have a hot water cylinder. This is typically the lowest upfront cost option for increasing in-home use, particularly if you install at the same time as your panel installation. It is a reliable and low maintenance piece of kit that directs your excess energy to power your immersion heater, instead of exporting to the grid.
On its own, excess solar energy is unlikely to meet all of your hot water needs, but it can help reduce your bills.
If you’re interested in using PV diverter, speak with your installer. They might also suggest increasing the number of panels on your roof to provide more electricity for your hot water needs.
Other options for renewable hot water include solar water heating, or fitting a whole-house heating system such as a heat pump or biomass boiler.
Costs, savings and financial support
With any domestic PV system, there will be times when the electricity you generate is more than you can use or store, so the surplus will be exported to the grid to be used by somebody else. If you want to be paid for exporting, you need to make sure you’re getting an export payment. If you were able to claim the feed-in tariff (this closed to new applications at the end of March 2019), then you will be getting export payments as part of that. If not, you need to find an energy company that will pay you for this surplus.
Following the closure of the Feed-in Tariff scheme to new solar PV system applicants in March 2019, the Smart Export Guarantee (SEG) was introduced to provide financial support to small-scale renewable energy generators for the electricity they export to the grid. The savings from solar PV with the SEG are considerably higher than without it.
In Great Britain, the Smart Export Guarantee pays you for the electricity you generate. In Northern Ireland, you can get paid for any surplus you export – usually estimated on the basis of how much you generate. Several organisations offer this service, so if you’re interested we recommend doing some research to find one that works for you.
Average cost The average domestic solar PV system is 3.5kWp and costs around £4,800. South England A 3.5kWp system in the south of England can generate around 3,700 kilowatt hours of electricity a year – that's the same amount of electricity as it takes to turn the London Eye 49 times. It will save around one tonne of carbon dioxide every year.
Scotland A 3.5kWp system in Scotland can generate about 2,850 kilowatt hours of electricity a year – that’s the same amount of electricity as it takes to turn the Falkirk Wheel 1,900 times. It will save approximately 0.8 tonnes of carbon dioxide every year.
PV installation costs can also be affected by:
typically, 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 about the same price per kWp, but PV tiles cost much more versus the equivalent panel system
panels built into a roof are more expensive than those that sit on top
This artice was originally posted on the Energy Saving Trust website, so to read more, click here. Don't think you can do solar? You can still go green by