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Generating renewable energy

Solar water heating


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

Solar water heating systems, or solar thermal systems, use free heat from the sun to warm water. A conventional boiler or immersion heater can be used to make the water hotter, or to provide hot water when solar energy is unavailable.

The hot water can be used throughout your home for bathing, showering and your hot taps.

How do solar hot water heating systems work?

Solar water heating systems use solar panels, called collectors, fitted to your roof. These collectors are filled with a special fluid, typically a mix of water and glycol (anti-freeze), which absorb heat from the sun and use it to heat up water stored in a hot water cylinder. A boiler or immersion heater can be used as a backup to heat the water further to reach the temperature you need.

There are two types of solar water heating panels:

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

Larger solar panels can also be arranged to provide some contribution to heating your home. However, the amount of heat provided is generally very small and it is not normally considered worthwhile.

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 during the winter months.

Reduced energy bills

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

Lower carbon footprint

Solar hot water 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


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.


Solar water heating systems can achieve savings on your energy bills. The saving will vary throughout the year, with many systems providing most of your hot water in the summer, but much less during the winter months.

Based on the results of a field trial we conducted across a range of household and system sizes, typical savings from a well-installed and properly used system are £60 a year when replacing gas heating, and £90 a year when replacing electric immersion heating. Savings will vary from user to user.

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 costs for solar water heating systems are generally very low. Most solar water heating systems come with a 5-year or 10-year warranty and require little maintenance.

Once fitted, your installer should leave written details of any maintenance checks that you can carry out from time to time to ensure everything is working properly.

Perhaps the most important thing for you to check for is whether there are any leaks. Leaks of the water-glycol mix will produce a strong smell (even if you can’t see any liquid). If you notice this, you should contact your installer.

If you are not getting hot water or the solar pipework is cold when the pump is running on warm, sunny days, you should contact your installer.

For peace of mind, some installation companies offer an annual service check.

You should have your system checked more thoroughly by an accredited installer every 3-7 years, or as specified by your installer.

It is likely that after this period, the glycol that protects your system in the winter months will need to be topped up or replaced, as it breaks down over time, reducing the performance of your system.

If you’re leaving for a summer break, you could consider leaving your solar water heating system running. Glycol degrades at excessively high temperatures and leaving the system running helps to reduce temperatures.

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, including what to look for when choosing an installer or product.

Last updated: 1 July 2021