Solar panels

The average solar panel system is around 4.5 kilowatt peak (kWp). The kWp is the maximum amount of power the system can generate in ideal conditions.

A 4.5kWp system typically covers between 20 to 30m² of roof surface area, typically using around 12 panels. 

An unshaded, south-facing roof is ideal for maximum performance. East or west facing roofs still work, but we don’t recommend installing 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 panel systems can minimise the impact of shading using ‘optimisers’. 

Solar 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 having an optimiser gives you extra opportunities to monitor your system’s performance. 

Solar 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. For example, there may be extra restrictions if you live in a: 

• listed building 
• conservation area 
• national park  

If you’re planning to install a solar panel 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 with the DNO for you. 

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

Yes, it’s okay to install panels on flat roofs. Panels on flat roofs are normally tilted up to help maximise energy production. 

It’s important that the panels don’t disturb 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 from leaks. 

Sometimes it might be recommended to renew the roof covering so that your roof remains in good condition while the solar panels are attached to it 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 be as south-facing as possible 

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. 

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

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

A heat pump 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 £11,000 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 energy generated by their solar panels. When you don’t use the energy from your panels it’s sent back into the 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 home appliances 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 for more than twice that amount per unit, it might make more sense to use the energy yourself instead of selling it. 

Time of use tariffs 

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: 

1. Store excess solar electricity in the day that you’d have otherwise lost. 
2. Use this stored energy to avoid more expensive tariff periods. 
3. Sell electricity from your battery at peak times, if you’re using one of the more innovative tariffs. 

Read our new research into how solar panels, batteries, heat pumps and smart tariffs can work together to save you money.