Solar Heating FAQ

Solar panel hot water heating systems – FAQ

Does a solar hot water system only work in summer?

Naturally, summer will provide the largest amount of solar hot water heating but a useful contribution will be provided by the other seasons as well. As an indication, a well sized typical installation will provide the following proportion of the household domestic hot water requirement:

  • Spring – 40 to 50% of domestic hot water requirements
  • Summer – 80 to 90% of domestic hot water requirements
  • Autumn – 40 to 50% of domestic hot water requirements
  • Winter – 20 to 30% of domestic hot water requirements


So over the whole year this translates to approximately half of the typical annual domestic hot water requirement.

Does solar heating only work when the sun is shining?

The solar heating technology works on solar radiation not just sunlight so it is effective on cloudy days as well.

How does solar energy provide domestic hot water heating?

Solar radiation is used to heat fluid in solar energy collectors on a south facing roof (or suitable surface) and that fluid is pumped through a domestic hot water storage cylinder. In that cylinder heat is exchanged between the collector fluid and your domestic hot water. Just like a boiler is used to heat your water.

Does a solar hot water system replace a normal boiler?

No the solar heating works along side your boiler reducing the need for the boiler to heat your domestic hot water. The boiler is also still needed for a central heating system.

Will I need a new hot water storage cylinder?

Most probably yes. Your existing cylinder is exchanged for a cylinder with two heat exchanger coils; one for the boiler and a second for the solar panels.

Is solar heating for domestic hot water worth it in the UK?

Typically a well designed domestic hot water solar heating system should provide approximately 50% of your domestic hot water heating needs of your home averaged throughout the year so it is worthwhile.

Will the solar collectors freeze in the winter

No – The solar panels are filled with a suitable heat absorbing liquid (a glycol and water mix) that won’t freeze in cold weather.

What happens when it is too cold for the solar heating system to provide hot water?

The solar heating system is equipped with a simple controller to regulate the flow of energy from the panels to the storage cylinder to maximise the use of the available free solar energy. The heat absorbing liquid will not be pumped around the system if it is not warm enough to be useful. Your standard hot water boiler will be providing all your hot water needs.

Where should the solar collector panels be positioned?

Ideally the solar heating panels should be facing a southerly direction at an angle of around 45 degrees. Where this is not possible the installation should move towards a westerly facing direction. East and North facing directions should be avoided.

Will I need planning permission to install solar heating panels?

Possibly – most local authorities will regard solar panels as similar to flush fitting roof-light windows, where planning permission may not be required. However seek the opinion of your local planning authority before any work starts on inbstalling the solar panel hot water system. Requirements vary from one authority to the next both with planning permission and building control procedures.

Are Grants available?

Yes – Under the Low Carbon Building Scheme the UK Government provides a grant to home-owners ) who want to install solar hot water systems. Homeowners can apply for a grant of up to £400 to assist in the cost of installing a solar panel hot water system.

Are their qualifying requirements before I can get a Grant?

Yes – You will need to demonstrate you have taken reasonable steps to ensure your house is energy efficient So before applying for a grant for a solar hot water system you are required you to have:

  • insulated the whole of the your loft to meet current building
  • installed cavity wall insulation (if you have cavity walls)
  • fitted low energy light bulbs in all appropriate light fittings
  • installed basic controls for your heating system to include a room thermostat and a programmer or timer.


When can I apply for a Grant?

You must obtain a quote from an accredited solar hot water heating installer before applying for the grant.

See for details of the DTI’s low carbon buildings grant.