Solar Thermal Panels

Solar thermal panels can be used to heat your water free of charge.

However newer renewable technology is available for this task, meaning solar thermal panels have become less popular.

Read our guide to solar thermal panels and other renewable water heating technologies below.

In This Guide:



What are solar thermal panels?

A solar thermal system uses specially designed solar panels which absorb energy from the sun. This energy is then used to power things like hot water heating systems, underfloor heating and swimming pools.

Solar thermal panels are usually made up of tubes, known as collectors, that are filled with a fluid similar to antifreeze, that warms up when exposed to the sun.

The warmed up fluid is then pumped to a cylinder containing heated water. The cylinder is usually connected to a normal electric immersion heater which can top up the temperature of the water if it is not high enough.

a diagram showing how solar thermal panels work

Depending on the size and location of your property, solar thermal systems can provide up to 70% of an average sized household's hot water needs.

This means that you can potentially save a lot of money on fuel. It is also possible to claim certain grants which pay you for the renewable energy you produce. So as well as providing an environmentally clean form of energy, a solar thermal system benefits consumers in a multitude of ways.



How much do solar thermal panels cost?

The cost of a solar thermal panel largely depends on the size of the system you want to install.

For an average sized system you can expect to pay between £3,000 and £5,000.

The table below shows the typical cost of installing popular solar thermal sizes:

System size
Size of household appropriate for
Typical cost of installation
Renewable Heat Incentive earnings per year
Typical fuel bill saving per year
Total Savings after 10 years
2 m sq
2 person
£2,600 - £3,200
£195
£57
£1,935
3 m sq
3 person
£3,000 - £3,600
£265
£62
£2,475
4 m sq
4 person
£3,400 - £4,200
£335
£65
£2,995
5 m sq
5 person
£3,900 - £4,500
£435
£74
£3,704
6 m sq
6 person
£4,200 - £5,000
£470
£79
£4,080




How much will I earn?

You earn and save money with solar thermal panels through:

  • The Renewable Heat Incentive - The government scheme pays you for producing renewable energy for 7 years. You receive these payments every quarter. Learn more below.
  • Energy bill savings - By using solar thermal panels to heat your water for free, you will make significant savings on your energy bills. Obviously the amount you save on your energy bills depends on how much free energy your solar thermal panels produce and how much you currently spend on energy. Higher consumption households will typically make bigger savings.

The table below shows typical savings and earnings for different sized systems and households.

System size
Size of household appropriate for
Renewable Heat Incentive earnings per year
Total Renewable Heat Incentive Earnings
Typical fuel bill saving per year
Typical fuel bill saving after 7 years
Total Savings after 7 years
Total Savings after 10 years
2 m sq
2 person
£195
£1,365
£57
£399
£1,764
£1,935
3 m sq
3 person
£265
£1,855
£62
£434
£2,289
£2,475
4 m sq
4 person
£335
£2,345
£65
£455
£2,800
£2,995
5 m sq
5 person
£435
£3,045
£74
£518
£3,563
£3,704
6 m sq
6 person
£470
£3,290
£79
£553
£3,843
£4,080




What grants are there for solar thermal panels?

The Renewable Heat Incentive is essentially a government grant for solar thermal panels. It pays households for the renewable energy that they produce through their solar thermal panels.

The scheme pays you every quarter for 7 years. Once you register for the scheme, you lock in your payments for the entire 7 years regardless of what happens to the scheme in the future.

The government are keen to cut spending on renewable energy, so it is highly likely that the scheme will be cut in the years ahead.

The table below shows typical earnings from the Renewable Heat Incentive for different sized solar thermal panels:

System size
Size of household appropriate for
Renewable Heat Incentive earnings per year
Total Renewable Heat Incentive Earnings
2 m sq
2 person
£195
£1,365
3 m sq
3 person
£265
£1,855
4 m sq
4 person
£335
£2,345
5 m sq
5 person
£435
£3,045
6 m sq
6 person
£470
£3,290




What alternatives are there to solar thermal?

A number of new technologies have now become more favourable for households wishing to heat their water through cheap renewable technology.

Smart Solar Devices

Many solar eco gadgets allow homeowners with solar panels to divert spare electricity to heat their water while the free electricity from the panels is not being used and would otherwise go back into the grid.

So not only could you earn and save around £404 a year with traditional solar panels, you could also heat your water for free and save an additional £250 a year on average using a smart device to divert spare solar electricity.

Costing around £500, a solar panel smart device will typically pay for itself in just 2 years which is much faster than solar thermal panels.

There are around 40 smart devices that perform this function. A product called Immersun is the most popular, with around 30,000 homes installing one to date.

Magic Thermodynamic Box

The Magic Thermodynamic Box is another popular alternative to solar thermal panels. The device works all the time regardless of the time of the day or weather, unlike solar thermal panels which only work during sunlight hours.

The Magic Thermodynamic Box is a solar assisted heat pump that saves you up to 80% of the energy used to heat your water.



Advantages of solar thermal

There are many advantages of solar heating. First of all, it is much cheaper than having a boiler running off coal, gas or oil. These are all fossil fuels which are running out quickly and so demand has gone up, followed by price. This also means that if they run out, your home will have a back up, as it is able to run on solar power.

For as long as the sun is around, your system will work, even on a cloudy or winter day. It is a renewable source of energy and much more environmentally friendly as it does not produce carbon emissions such as carbon dioxide, which contribute to global warming.



Disadvantages of solar thermal

Solar thermal panels are relatively expensive and take around 10 years to return on investment. Newer technology such as smart solar devices that heat your water tank are already starting to make solar thermal panels obsolete.

Solar thermal panels require exactly the right location and conditions to work efficiently, which means many properties in the UK are unsuitable.



Can I use solar thermal panels to heat my swimming pool?

Solar thermal panels can be used to heat your pool. However, unless you install a large solar thermal system, it is unlikely that all your pool heating costs will be eradicated by installing solar thermal panels.

If you have a pool which you want to heat with free renewable energy, you will also want to consider alternatives to solar thermal panels. These have started to make solar thermal panels obsolete.



What solar thermal mounting options are there?

There are three principal mounting systems which are available for the installation of a Solar Thermal array:

A flush mounting frame is normally constructed from high quality stainless steel to withstand the extremes of weather and to ensure long lasting functionality. A standard flush mount frame is suitable for use with both flat plate collectors and evacuated tube collectors and can be fitted to integrate into the roof in the manner similar to a Velux window.

Using an angled frame mounting system provides the potential to direct the solar array to allow for optimum energy capture. Evacuated tube collectors may be directed to an angle between 28-68 degrees and flat panel solar collectors can also be adapted to maximise their potential. Free standing angle framed structures are always used for the installation of ground, wall or flat roof erections.

Ballast mounting is a specific design for use in applications where an evacuated tube thermal system is to be installed onto a roof which cannot be compromised. The array is integrated into an angled frame and ballasted blocks are then used to anchor the structure firmly to the roof without the need to penetrate the surface.



Commercial solar thermal

The types of projects that can benefit from a professionally designed and fitted commercial solar heating system are schools, hotels, factories and office blocks. With solar heating reported as offering a quicker payback than solar PV panels, many commercial ventures have opted for solar heating as a worthwhile energy saving investment. The number of solar heating panels required for a commercial building will depend on the length of pipe being used to deliver the water to the building, the size of the calorifier (cylinder) and the angle of the solar panels.

Large swimming pools can be extremely expensive to heat, both indoor and outdoor, and commercial solar heating can be used to significantly reduce the cost of energy and reduce the negative impact such commercial activities can impose on the environment.

To help encourage small to medium sized businesses to invest in commercial solar heating the Carbon Trust is offering interest free loans of up to £100,000 in the UK and up to £200,000 in Northern Ireland. It is available when a SME upgrades or replaces a central heating system with energy saving and environmentally friendly alternatives.

The Carbon Trust is a not-for-profit company set up by the UK government to encourage businesses and the public sector to invest in low carbon technologies and help reduce carbon emissions. The Carbon Trust also aims to help increase SME's profitability by promoting the use of commercial solar heating and similar technologies to reduce fuel bills whilst lowering the contribution to global warming.


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