Solar Thermal project guide

What is it?

Solar water heating systems, or 'solar thermal' systems, use 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.

What is it suitable for?

Properties most likely to benefit from installing a Solar Thermal system have a high hot water demand and may be dependent on oil or LPG. Solar Thermal may also be an attractive option if roof space is too restrictive for Solar PV.

Solar Thermal combines well with other renewable heating technologies, when using a thermal store.

What are the benefits?

  • It produce between 50% – 70% of your hot water (depending on water usage)

  • Works well with other renewable systems

  • Biggest carbon reduction per square meter

  • Relatively low cost and simple to install

  • Generates a tax-free income from the RHI

How does it work?

A solar thermal system uses solar panels, called collectors, fitted to your roof. These collect heat from the sun and use it to heat up water which 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:

  • Evacuated tubes
  • 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.

How does it compare?

Solar PV:

  • They provide clean energy for over 30 years.
  • They come with a warranty of 25 years or more.
  • They can provide you with 60% or more of your household energy needs, depending on your consumption and the size of the system.
  • They generate the most power in the summer, when the sun is strongest.
  • They can provide enough energy to power high-consuming appliances like a refrigerator, tumble dryer or air conditioner.
  • They protect your roof, thereby extending its lifespan.
  • They can be integrated into your roof for optimum aesthetic value.

Solar Thermal:

  • They are up to 70% efficient in collecting heat from the sun.
  • They will cut your gas and electricity usage.
  • They require less space on your roof than a solar pv system.
  • The up-front cost of installation is less than a solar pv system.
  • It takes less time to recover your initial cost, typically only 3-5 years.
  • The technology is less complex and very dependable.
  • The technology is widely used in other parts of the world.

Costs & Savings


  • A typical Solar Thermal system will cost around £3,000 to £5,000 fully installed, dependent upon the model chosen, and the size of the system.


  • Independent figures from the Energy Saving Trust suggest in standard 4-bedroom house you should be able to save between £60 to £125 per year compared to Gas, Oil, Electricity and LPG systems.
  • In addition, you should be able to earn up between £195 and £470 per year through the Renewable Heat Incentive.