Solar Thermal

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 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:

  1. Evacuated tubes
  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 boilers 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.

 Costs, savings and financial support

The cost of installing a typical solar water heating system is £4,000 – £6,000. Savings are moderate – the system can provide most of your hot water in the summer, but much less during the winter months.


Maintenance costs for solar water heating systems are generally very low. Most solar water heating systems come with a ten-year warranty and require little maintenance. Once fitted Isle-eco will leave written details of any maintenance checks that you can carry out from time to time to ensure everything is working properly.

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. This cost of replacing the anti-freezer is usually around £150 dependant on system size.

In a well maintained system, pumps can last for more than 10 years and cost approximately £90 to replace.

Swimming Pools

Solar thermal is ideal for providing heat for swimming pools. By harnessing the sun a thermal system can provide 80% of your pool’s annual heating needs and can be installed to complement the majority of existing heating systems or to heat the pool independently.

The pool ideally needs to be within 25 metres of the house, with the system mounted either on the roof of your building or by the poolside. We would also recommend that the solar thermal system is linked to your building’s main heating system ensuring that in winter the system can cover some domestic hot water needs, and in summer heat both the pool and the house.