Helping UK homeowners save money on their heating

Solar Thermal: Benefits, Costs and Grants

Solar thermal panels use energy from the sun to provide your home with a free supply free hot water. This hot water can then be delivered to baths, taps, showers and even a wet central heating system.

Not only will this help to lower your heating bills, you’ll also be reducing your property’s carbon footprint. Which is good news for the environment.

Solar Thermal technology explained

Solar thermal, or solar water heating technology, allows you to produce hot water for your home using free heat from the sun. They’re made up of panels or collectors, installed outside in prime position to collect sunlight, absorbing heat from the sun before using it to heat water for your home.

This is opposed to solar PV panels which absorb convert energy from the sun into electricity.

Installing a solar water heating system in your home can greatly reduce the amount of money you spend on heating water, the amount of carbon your home produces and can actually earn you money through the government’s Renewable Heat Incentive scheme.

How does solar water heating work?

Solar thermal panels are most likely to be installed on your property’s roof – the prime position to abosorb as much sunlight as possible. Here’s how they work:

  1. Cold water is fed into a tank or cylinder in your home from the mains
  2. Solar collector panels on your roof include a fluid which is heated when exposed to sunlight
  3. This heated liquid is then passed down into your water tank where it passes through a coil and heats the water
  4. This hot water can then be used in your home. A backup boiler or immersion heater can top up the hot water supply on cloudy days or when your need for hot water is greater

solar thermal diagram

Advantages of solar thermal

Cheaper Energy Bills

A solar water heating system can produce between 40-70% of the hot water needed by a 4 person household with free energy from the sun. This means you will need to use your boiler less and therefore will pay your energy supplier less, saving you money on bills.

Earn Money Through RHI Payments

If your system meets certain installation conditions, the government will pay you money for the renewable energy you generate under the Renewable Heat Incentive (RHI) scheme.

Lower Carbon Emissions

Using free, renewable solar energy rather than gas, oil, coal or LPG will help to reduce your home’s carbon footprint.

No Running Costs

After the upfront cost of the installation there are no running costs for a solar water heating system other than professional servicing every 3-5 years.

Easy to Maintain

Solar water heating systems are very low maintenance. Aside from a professional servicing every few years you should only need to make an annual check of the system for leaks.

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Types of solar thermal collectors

When deciding which solar thermal collectors to invest in you will find two main types to choose from: flat plate or evacuated tubes. They are both panels which are fitted to your roof in most cases. They deliver largely the same results in terms of hot water production but do so using slightly different processes.

Flat plate collectors: These panels are like insulated metal boxes with plastic or glass top. They contain thin tubes of a kind of antifreeze liquid which heats up when exposed to the sun.

Evacuated tube collectors: These panels include metal absorber tubes of antifreeze liquid which are inside glass tubes. This minimises heat loss as the extra glass tube creates a vacuum.

hot water from tap

Disadvantages of solar thermal

You will still need a boiler

While a solar water heating system will provide a significant amount of your hot water it is unlikely to deliver all the water you need. You will need to top up with a boiler or immersion heater when the sun is hidden by cloud, especially during the winter months.

Won’t supply all your appliances

Solar water heaters won’t supply electric showers, cold-fill washing machines or dishwashers; if you don’t use a lot of hot water other than this you may not find a solar system makes much difference to your hot water use.

Not suitable for (most) combi boilers

A solar water heating system requires a tank of cold water usually found in homes which use System or Regular boilers; a Combi boiler is supplied water directly from the mains and generally will not accept pre-heated water.

Changes to your heating system may be needed

If your current water tank or cylinder is not solar compatible this will need replacing. Also if your heating system is fed water from a large feed tank in the attic which relies on gravity you may need an extra pump installed so heating and hot water can run at the same time.

Can be costly to install

The average cost of installing a solar water heating system is between £3,000 – £5,000 which is a considerable investment. However, it’s important to weight these costs up with the potential long term savings you’ll be making on your heating bills.

calculator and coins

How much does solar thermal cost?

The cost of installing a solar water heating system for a family of 4 could cost between £3,000 – £5,000 but this will vary from home to home. Generally, professionals recommend around 1 metre squared of panels per person using the system.

As with all home improvements the price will also be impacted by the simplicity or complexity of the installation. The installer will need to integrate the technology into your existing plumbing and sometimes scaffolding may be needed.

Size of System (1m2 per person) Average Cost of Installation
2m2 £2,500 – £3,000
3m2 £3,100 – £3,600
4m2 £3,700 – £4,200
5m2 £4,300 – £4,800
6m2 £4,900 – £5,400

However, there are annual savings to be made on reduced energy bills which make the cost of installation more palatable long term. The amount you’ll save will mainly depend on the type of fuel your solar heat is replacing. The Energy Saving Trust estimates the following savings in terms of fuel bills and carbon emissions but these will vary from home to home.

Existing Heating System Potential Fuel Bill Savings (annual) Potential CO2 Savings (annual)
Gas £50 270kg
Oil £55 350kg
Coal £65 5450kg
Electricity £80 390kg
LPG £95 310kg

Solar water heating grants & incentives

Until 31st March 2022, you can receive a Green Homes Grant to cover up to two-thirds of the cost of installing solar thermal panels. Through the Green Homes Grant, you will receive a voucher of up to £5,000 (£10,000 for low income households).

If your solar water heating system meets certain installation conditions you will be entitled to earning money through the government’s Renewable Heat Incentive (RHI) scheme.

For every unit of energy you generate through your solar water heating system you will receive a payment. The payments are made on a quarterly basis over 7 years. For solar thermal heating systems accepted onto the RHI between 1st July 2020 and 30th September 2020, you will receive 21.36p per kilowatt-hour. This is the highest payment of all renewable heating systems eligible for the RHI.

Solar thermal panel manufacturers

The best solar thermal panels are manufactured by Viessmann, Dimplex, Solar UK and Worcester Bosch. The table below takes a look at the evacuated tube and flat plate collectors manufactured by each of them.

Manufacturer Evacuated Tube Collectors Flat Plate Panel Collectors
Viessmann Vitosol 200T, 300T, 200TM, 300TM Vitosol 100FM or 200FM
Worcester Bosch N/A Greenskies Solar Lito or Greenskies Solar Lifestyle
Kingspan Thermomax HP400/DF400 or Varisol Kingspan Flat Plate Panels
Dimplex SOLCDF22, SOLCDF32 SOLC201, SOLC220

solar installer

Solar thermal panel installation

Where to install

The ideal place to install solar water heating panels is on a south facing roof but they are still effective facing south east or south west. The best angle is between 20-50 degrees from horizontal but a frame can be fitted if your roof isn’t angled correctly. In some cases it is possible to install the panels on the ground as long as they aren’t shaded.

Planning permission

Unless you live in a conservation area or listed building it’s unlikely you’ll need planning permission as solar panels are usually classed as a ‘permitted development’ but you may want to check with your installer and local authority to be sure.


Solar collector panels are usually covered by a warranty of up to 10 years and, unless your system isn’t working effectively, should only need professional servicing every 3-5 years.

Get free solar thermal installation quotes

If you think a solar water heating system could be the right choice for your home, your next step is to contact professionals. They will be able to advise you if a system could be of benefit to your home in terms of how your hot water is currently produced, how you use it and potential benefits.

Visit our sister website, Solar Guide, to get free quotes from up to 3 solar thermal installers in your local area. We recommend comparing quotes from at least 3 professional installers so you can compare not only their advice but also the prices.

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