Skip to main content
Generating renewable electricity

Solar water heating

Benefits

  • hot water throughout the year
  • reduced energy bills
  • lower carbon footprint

What is solar hot water?

Solar water heating systems, or solar thermal systems, use energy from the sun to warm water for storage in a hot water cylinder or thermal store. Because the amount of available solar energy varies throughout the year, a solar water heating system won’t provide 100% of the hot water required throughout the year. A conventional boiler or immersion heater is normally used to make up the difference.

Larger solar hot water arrays can also be arranged to provide some contribution to heating your home. However, the amount of heat provided is generally very small (less than 10% of the home’s heating requirement), so it is not usually considered worthwhile.

Most solar hot water systems are just designed to provide the hot water you use for bathing, showering and hot taps.

How do solar hot water heating systems work?

Solar water heating systems use panels or tubes, called solar collectors, to gather solar energy. The solar collectors convert the infra-red portion of visible light into heat. They are filled with a mix of water and glycol. This fluid is pumped round a circuit, which passes through the hot water cylinder.

There are two types of solar water heating collectors:

  • Evacuated tubes – a bank of glass tubes mounted on the roof tiles.
  • Flat plate collectors – fixed on the roof tiles or integrated into the roof.

Benefits of solar water heating

Hot water throughout the year

The system works all year round, though you’ll need to heat the water further with a boiler or immersion heater, especially during the winter months. In the summer, it should provide around 90% of your hot water requirements, dropping to around 25% in the winter.

Reduced energy bills

Sunlight is free, so your hot water costs will be reduced.

Lower carbon footprint

Solar water heating is a renewable heating system and can reduce your carbon dioxide emissions.

Is solar water heating right for your home?

To tell if solar water heating is right for you, there are a few key questions to consider:

Costs, savings and financial support

Costs

The cost of installing a typical solar water heating system is around £3,000 to £5,000. Costs will depend on whether you choose evacuated tube or flat plate collectors, as well as the size of the system.

Savings

Solar water heating systems will normally be designed to provide roughly half your hot water requirement. The saving will vary throughout the year, with systems providing nearly all your hot water in the summer, but less during the winter months.

Financial support

You may be able to receive payments for the heat you generate from a solar water heating system through the UK Government’s Renewable Heat Incentive (RHI).

Maintenance

Solar hot water systems are typically low maintenance, but it is important to follow your installer’s guidance. Solar water heating systems installed by an MCS contractor will come with a five-year workmanship warranty and 10 years or more for the panel warranty.

Once fitted, your installer should leave written details of any maintenance checks that you can carry out to ensure everything is working properly. This normally includes checking a pressure gauge to ensure there are no leaks.

If you are not getting hot water or the solar pipework is cold when the pump is running on warm, sunny days, you should check the control panel for warnings, and then contact your installer.

For peace of mind, some installation companies offer an annual service check. This should cost less than a full service and takes around 10-20 minutes.

You should have your system checked more thoroughly every five years. This will involve draining and flushing the system and replacing the fluid. This is because over time the anti-freeze protection offered by the glycol will reduce. Leaving it for longer than five years can be detrimental to the system’s efficient operation.

If you’re leaving for a summer break, you should leave your solar water heating system running. Some solar controllers offer a ‘holiday’ function that will help protect the system if you are away for a few days – but don’t forget to turn it off when you return.

Choosing an installer and system

There’s a lot to consider before installing a renewable system such as solar water heating, but having one will help reduce your energy bills and household carbon footprint.

Our helpful guide offers advice on things to consider when installing a renewable system.

Last updated: 20 October 2021