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Solar water heating

Solar water heating systems, or 'solar thermal' systems, use free heat from the sun to warm domestic hot 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 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 once you've paid for the initial installation your hot water costs will be reduced.
  • Lower carbon footprint. Solar hot water is a green, renewable heating system and can reduce your carbon dioxide emissions.

How do solar water heating systems work?

Solar water heating systems use solar panels, called collectors, fitted to your roof. These collect heat from the sun and use it to heat up water that is stored in a hot water cylinder. A boiler or immersion heater can be used as a back up to heat the water further to reach the temperature you want.

There are two types of solar water heating panels:

  1. Evacuated tubes - a bank of glass tubes mounted on the roof tiles.
  2. 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 as well. However, the amount of heat provided is generally very small and it is not normally considered worthwhile.

Is solar water heating right for your home?

Things to consider


  • Do you have a sunny place to put solar panels? You'll need around five square metres of roof space which faces East to West through South and receives direct sunlight for the main part of the day. The panels don't have to be mounted on a roof however. They can be fixed to a frame on a flat roof or hang from a wall.
  • Do you have space for a larger, or an extra, hot water cylinder? If a dedicated solar cylinder is not already installed then you will usually need to replace the existing cylinder, or add a dedicated cylinder with a solar heating coil.
  • Is your current boiler compatible with solar water heating? Most conventional boiler and hot water cylinder systems are compatible with solar water heating. If your boiler is a combination boiler (combi) and you don't currently have a hot water tank, a solar hot water system may not be compatible.

A competent accredited installer will be able to assess your home and help you choose the best setup to meet your needs.

Find out about planning permission and making the most of your solar hot water system.

Costs, savings and financial support


The cost of installing a typical solar water heating system is £4,000 - £5,000 (including VAT at 5 per cent for 3.6m2 system). Savings are moderate - the system can provide most of your hot water in the summer, but much less during colder weather.


Solar water heating systems can achieve savings on your energy bills. 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 per year when replacing gas heating and £70 per year when replacing electric immersion heating. Savings will vary from user to user.

Existing system

Fuel bill savings (£/year)

Carbon dioxide savings (kgCO2/year)



295 kg



410 kg



660 kg



205 kg



340 kg

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).

Household size

Assumed system size

Renewable Heat Incentive (RHI) payment (£/year)

1 April 2020 to 30 June 2020

 2 person household

 2 m2


 3 person household

 3 m2


 4 person household

 4 m2


 5 person household

 6 m2


 6 person household

 6 m2


Find out more about how we made these calculations.


Maintenance costs for solar water heating systems are generally very low.

Most solar water heating systems come with a five-year or ten-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 anti-freeze 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 then 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 of time, the anti-freeze that is used to protect your system in the winter months will need to topped up or be replaced as it breaks down over time reducing the performance of your system.

Anti-freeze lasts better if the solar water system is used throughout the year and not left unused during the warmest weeks of the year.

Choosing an installer and system

Our 'installing renewables' web page covers the key points you need to consider when installing a renewable system, including what to look for when choosing an installer or product.