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Solar panels: a comprehensive guide - Energy Saving Trust

Solar panels, also known as photovoltaics (PV), capture the sun’s energy and convert it into electricity to use in your home.

Installing solar panels lets you use free, renewable, low carbon electricity. You can sell surplus electricity to the grid or store it for later use. Insulated Endshield

Solar panels: a comprehensive guide - Energy Saving Trust

According to low-carbon certification organisation MCS , there were more than 183,000 solar panel installations across the UK in 2023. This is a third higher than 2022, showing that solar is an increasingly popular renewable technology.

And, against the backdrop of unstable energy costs, it’s a good time to consider taking advantage of the free, renewable energy that solar panels provide.

The cells don’t need direct sunlight to work and can even work on cloudy days. However, the stronger the sunshine, the more electricity generated

Solar panel systems tend to be made up of between six and 12 panels, with each panel generating around 400 to 450W of energy in strong sunlight.

You can use our online assessment tool, Go Renewable, to find out what renewable technologies are suitable for your home.

There are also a few things to consider before you commit to a solar panel installation:

The average solar panel system is around 3.5 kilowatt peak (kWp). Most panel systems typically cover between 10 to 20m2 of roof surface area.

Use our solar panel calculator to get an idea of what size solar panel system would be suitable for your home.

What’s the difference between a kilowatt peak and a kilowatt hour?

Kilowatt peak refers to the maximum total power output of a solar panel system. A kilowatt hour is a measurement of the amount of energy generated by the system.

In the UK, one kilowatt peak of solar panels facing south generate between 800 and 1000 kilowatt hours a year. This figure will change depending on where in the UK the solar panels are installed.

An unshaded, south-facing roof is ideal for maximum performance. East or west facing roofs still work, but we don’t recommend installing solar panels on a north facing roof.

A system facing east or west tends to get around 15-20% less energy than one facing directly South.

Nearby buildings, trees or chimneys could shade your roof and have a negative impact on the performance of your system.

Finding an unshaded spot is best, but sometimes shading is unavoidable. Some solar PV systems can minimise the impact of shading using ‘optimisers’.

Solar panel optimisers help improve the overall performance of your solar panel system. So, if one panel is shaded, it doesn’t impact how much electricity the other panels can generate.

If your roof doesn’t have shading, optimisers won’t help you generate more electricity. But they also give you extra opportunities to monitor your system’s performance.

Solar PV panels on houses are considered ‘permitted development’ and don’t usually need planning permission. But there are exceptions so it’s best to check with your local planning office for guidance. If you live in a listed building, conservation area or national park, there may be additional restrictions.

If you’re planning to install a solar PV system in your home, you must register it with your Distribution Network Operator (DNO). The DNO is the company responsible for bringing electricity to your home. Usually, your installer will register the device for you.

The UK Government has advice on how to register your new energy device in England, Scotland and Wales.

In Northern Ireland, your installer will register your solar panel system with NIE Networks.

Yes, it’s okay to install panels on flat roofs. Solar panels work best when angled towards the sun, so panels on flat roofs are normally tilted up to help maximise energy production.

It’s important that any solar panel system maintains the integrity of the roof covering to keep it watertight. For this reason, many systems are weighted down rather than fixed through the roof covering.

If you have a system that’s weighted down, the roof needs to be strong enough to deal with the added weight. If the roof isn’t strong enough, use appropriate fixings to ensure rain can’t cause any damage.

Sometimes it might be recommended to renew the roof covering so that you get the best possible roof integrity and solar panel performance. Even though it may add to the cost, the overall solution will be cheaper in the long run.

Yes, you can install panels in the garden on a suitable frame. Make sure they don’t get shaded by nearby trees and buildings, and they should face as close to south as is practical.

One advantage of mounting panels in the garden is that it’s easy to keep them clean. But you also need to be more careful about rodents and other physical damage.

Yes, you can install panels on an outbuilding. It’s important to make sure that the building roof is strong enough.

If the building doesn’t have its own electricity supply already then you should factor this in when looking at the total cost of the system.

Sunlight is free, so once you’ve paid for the initial installation, your electricity costs will be reduced.

Solar electricity is low carbon, renewable energy. A typical home solar panel system could save around one tonne of carbon per year, depending on where you live in the UK.

That’s the equivalent of driving 3,600 miles, or from London to Bristol 30 times.

The average domestic solar panel system is 3.5kWp and costs around £7,000. The amount you pay is influenced by:

Some of the installation costs can be shared if you already have scaffolding up for roof repairs or if you’re building a new house.

The cost of ground-mounted solar panel systems is more difficult to predict, as there are more variables such as:

Costs can vary between installers and products, so we recommend getting quotes from at least three installers.

Make sure the installers you look at are MCS-certified, which ensures they adhere to a strict code of conduct. You can find installers on the MCS website.

There aren’t any specific solar panel grants. But you may be able to get funding as part of other government schemes.

Get in touch with your local council or energy supplier to see if they offer funding under the Energy Company Obligation (ECO) scheme.

Read our advice on renewable energy funding for Scottish residents.

Get in touch with NI Energy Advice to find out what funding options are available for you.

The amount you could save using a solar panel system depends on a few things:

t CO2 saved/year = 0.83. Updated to reflect April 2024 figures. 

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t CO2 saved/year = 0.75. Updated to reflect April 2024 figures. 

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t CO2 saved/year = 0.73. Updated to reflect April 2024 figures. 

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t CO2 saved/year = 0.66. Updated to reflect April 2024 figures. 

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t CO2 saved/year = 0.74. Updated to reflect October 2023 figures.

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Solar panels on their own offer lower electricity bills and low carbon energy. But they’re at their best when combined with other renewable technologies.

Instead of exporting surplus electricity, you could store it for later use. Battery storage lets you use your solar electricity when your panels aren’t generating energy, reducing the need to import electricity from the grid during peak times.

Battery storage tends to cost around £5,000 to £8,000.

A heat pumps is a low carbon heating system that’s powered by electricity. Using a solar panel system to power the heat pump, you can lower both your electricity and your heating bills.

The most common type of heat pump are air source heat pumps, which cost around £14,000 to install.

Depending on where you live, there are different funding options available to get a heat pump. For more information, check out our heat pump hub.

Electric vehicles (EVs) are essentially electric batteries on wheels. You can charge your electric car or van during the day while the panels are generating electricity, reducing your fuel costs.

Most people aren’t at home in the middle of the day to take advantage of the solar energy generated by their solar panels. When you don’t use the energy from your solar panels it’s sent back into the electricity grid

If you work from home, you’ll naturally use some of the energy yourself. If you’re away during the day, you’re less likely to use this energy, unless you set timers for your dishwasher and washing machine to run during this time.

Typically, you ‘ll get around 12p for every unit that you don’t use yourself through the Smart Export Guarantee. But since you’d normally buy electricity at around 28p a unit, it makes more sense to use the energy yourself instead of selling it.

Adding a battery to your solar panel system allows you to store any unused solar energy in the day and use it at night instead. For every unit of electricity stored in a battery and used at night, it will save you around 14p.

Some energy providers also offer time of use tariffs, which encourage you to use electricity outside of peak hours when electricity is cheaper. If you have a battery and a time of use tariff it allows you to:

During daylight hours, you’ll be generating electricity even on cloudy days. But you’ll have to supplement this by importing electricity from the grid:

Reducing your electricity use can help reduce your reliance on imported electricity. It also helps lower your electricity bills and carbon footprint even further.

For more tips to reduce your energy use, see our energy saving quick wins.

Instead of sending surplus electricity to the grid, a PV diverter switch can power the immersion heater in your hot water tank, storing hot water for you to use later. On its own, excess solar energy is unlikely to meet all your hot water needs, but it can help reduce your bills.

A PV diverter switch installation could add around £800 to your installation costs. You’ll need to replace your diverter after around 12 years.

If you’re interested in using PV diverter, speak with your installer. They might also suggest increasing the number of solar panels on your roof to provide more electricity for your hot water needs. Here are the average annual savings when using a PV diverter with your solar panel system:

Your solar panels should last 25 years or more. But if you have a solar PV inverter, you need to replace this after around 12 years. This costs around £800, depending on system size and the manufacturer. Some inverters have online monitoring functions and can warn you by email if the system fails.

Most inverters have warranties of five years as a minimum, which you can often extend up to 15 years. Speak to your installer about the likely lifespan and benefit of an extended warranty.

You might find that a 15-year warranty costs almost as much as a replacement inverter, so consider it carefully.

Solar PV systems need little maintenance. Keep an eye on nearby trees and keep them well trimmed to minimise shading of the array where possible.

In the UK, rain will clean your panels if they’re tilted at 15 degrees or more. Debris is more likely to build up if you have ground-mounted panels, or if you live in an area with more dust in the air. In these cases, you might need to have the panels cleaned occasionally.

Your solar panel installer should leave written details of any maintenance checks that you should conduct to ensure everything is working properly. This should include details of the main inverter fault signals and key troubleshooting guidance.

Ideally, your installer should demonstrate this to you once the system has been installed. Speak to your installer for exact maintenance requirements before you commit to installing a solar PV system.

Sign up to Energywire, our monthly newsletter full of news, advice and tips on energy saving and renewable energy options.

Use the calculator to get an idea of the benefits you may see from installing solar panels at home.

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