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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 - 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?

  • 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.

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 £55 per year when replacing gas heating and £65 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)

         Gas                                                                £55                                                                  260 kg

          Oil                                                                 £70                                                                  340 kg

         Coal                                                               £65                                                                  520 kg

         Electricity                                                     £65                                                                  220 kg

         LPG                                                               £95                                                                  300 kg


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.

This cost of replacing the anti-freezer is usually around £100.

The other thing that your installer should check is the pump. In a well maintained system, pumps can last for more than 10 years and cost approximately £90 to replace.

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

Choosing an installer and system

There is a lot to consider before and after installing a renewables system, but having one at home will help reduce your energy bills and household carbon footprint.

Before installing a renewables system

1. Find a reputable installer

Its recommend you use an installer who is certified under the Microgeneration Certification Scheme (MCS) and uses MCS-certified products.

All installers or suppliers should be able to provide a detailed breakdown of the specification and costs of their proposed system. They should also be able to:

  • Explain how they have calculated the size of the system to be appropriate for your needs.

  • Supply clear information and operating instructions.

  • Explain how you should maintain your system.

  • Provide an estimate of how much heat and electricity will be generated by any proposed system, and illustrate what this means in terms of your current energy needs.

  • Provide an estimate of the savings you could make after installation.

2. Get a quote

Its recommend you get at least three quotes from three different installers. Beware of heavy-handed sales techniques, such as pressure to sign on the day, high prices with large discounts for signing on the spot, or bogus monitoring scheme discounts.Don’t compare installers on cost alone – the cheapest may not be the most appropriate.

Check your quotations for the following:

  • Will the installer project manage the whole job or will you need to arrange and pay for other trades such as electricians, plumbers or ground work contractors?

  • Do the prices cover the distribution system (radiators and associated pipework) and the safe removal and disposal of any existing equipment, for example your old boiler?

  • Do prices cover the cost of commissioning the system? All accredited installers are certified to commission systems once fully installed to ensure that they are fit for purpose.

  • Make sure that you receive a Commissioning Certificate from the installer.

  • Available options e.g. size, fuel type, hot water storage, and maintenance cycles.

  • The efficiency values of the system.

  • Payment options - your deposit should not be more than 25 per cent of the full cost. You should check that this will be protected with insurance.

  • For heating systems, ask whether the cost of integration with your home’s heating system, or a proposed heating system, is included.

3. Check planning permission and building warrants

Depending on the kind of property and installation, you may also need to get planning permission or a building warrant from your local planning authority. Make sure you have the right permissions in place before beginning installation.

If your home is a listed building you will almost certainly require consent from your local authority. You should always check with your local planning department to find out if planning permission or building warrants are required: You should also check that the installation complies with building regulations in your area:

4. Check your insurance policy

Check with your home insurance provider to make sure your policy covers the changes to your home, and make any adjustments you need. Some policies cover the more common systems, such as solar PV.

After installing a renewables system

1. Check your MCS certificate

Once the renewables system has been commissioned you should receive an MCS installation certificate from your installer. MCS requirements state that your MCS installer should have registered your system within ten working days of the system being fully installed. Householders must use an MCS certified installer and product for most funding schemes.

2. Organise a follow-up EPC

You may wish to get a follow-up Energy Performance Certificate (EPC) carried out to update the energy efficiency rating of your property.

An EPC is now required if you wish to rent your property in the UK or sell your house in Scotland. EPCs are also required to pre-qualify for certain government financial incentive schemes for renewables systems and insulation.

If you get any energy saving measures retrofitted in your property such as wall, floor or loft insulation which will not be visible, it is very important to keep evidence of this work. Take photos before and after installation, keep receipts of materials and builders' invoices and building warrant plans.  

If an EPC surveyor cannot visually see the measure because it's inaccessible they will need to see documentary evidence of the work undertaken in order to validate the EPC. 

If you do not have evidence of retrofit insulation, this insulation cannot be factored into the EPC rating and will be ignored. Instead the level of insulation will be assumed based on the building’s age. This may significantly affect the EPC energy rating and the rating may not be as high as it could be.

3. Claim financial support for which you applied

Check to see what paperwork is required to complete your application. Most schemes will require your MCS certification to process your claim.

4. Learn about your system

Make sure your installer explains how your system and its controls work before they finish, and that they hand over any manuals that come with the system.

This is a standard part of the installation process and any competent installer should be happy to take you through this.

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