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1,567 reviews

What is a Solar Thermal Heating System?

Nick Geary
By: Nick Geary
Updated: 6th July 2022

What is a Solar Thermal Heating System
In many ways solar thermal is similar to solar PV, but rather than turning the sun's energy into electricity this system uses it to heat your water. This solar heated water can supply both a wet central heating system as well as your taps, baths and showers.

By using the sun's energy (which is free) to heat your water you will need to use your boiler less. This means cheaper heating bills, lower carbon emissions and less strain on your boiler.

How does solar thermal work?

  1. Solar thermal panels (also known as collectors) are fitted to your roof. The panels include tubes of fluid which absorb heat from the sun's energy.
  2. This hot fluid travels down into your home and the heat is transferred to your hot water storage tank via a heat exchanger.
  3. This hot water then travels around your pipes as it would in a standard wet heating system.

Types of solar thermal panels

When choosing which solar thermal panels, you'll have 2 types to choose from: flat plate or evacuated tubes.

Flat plate collectors

Flat plate collectors include metal tubes and look very much like solar PV panels i.e. they are flat panels with a dark glazed surface. The tubes inside are usually copper or aluminium and filled with fluid. The fluid, heated by the sun's energy, then travels down into your home where it can heat your water.

Evacuated tube collectors

These panels look more like a series of glass tubes in a parallel row. They include a vacuum to add an extra layer of insulation and are generally regarded as the more energy efficient and attractive choice. However they are often more costly.

If you’re sold on solar and you want to get quotes for solar thermal heating installation prices, you can do so below.

How much hot water will I get?

A solar thermal system can produce between 40-70% of the hot water required by a family of 4.

It's likely that during the coldest months your hot water will need to be supplied by a traditional boiler or an immersion heater, but the solar thermal system should significantly reduce how often you need to use them. By using them less often you can reduce how much you spend on gas, oil or electricity and – as they're not working as hard – they should last much longer.

In terms of how much of your hot water could be provided by solar thermal, it's difficult to calculate. Clearly, the bigger your house the more radiators and bathrooms you will need to supply, but there are a few other things to consider as well

How much hot water do you use?

No two families are the same but, if you can adapt your routine to use hot water in the evening when the water has been heating all day, you are going to get more benefit from your system. There will be less hot water to use when the heating is running (unless you have separate controls for your heating and hot water).

How much sunlight is available?

Although solar thermal will still generate some hot water in cloudy weather they are going to be more effective in the summer months, so your hot water supply may be a little unpredictable at times.

How much hot water can you store?

The size (volume capacity) of your hot water cylinder will dictate how much of your solar generated hot water you can store. Both your cylinder and pipework should be insulated to prevent heat loss.

Is solar thermal right for you?

  • A solar thermal system can be integrated into your existing heating system or installed as part of a renovation or new build. In the majority of cases you don't need planning permission for a solar thermal system as it's a 'permitted development'. However, it's always best to check with your local authority.
  • Solar water heating systems could save you money on your bills. Find out more about the pros, cons, costs and potential savings of solar thermal.
  • You'll need to have at least 5 square metres of roof space ideally facing east to west through south with as much exposure to direct sunlight as possible. In some cases they can be fixed to a wall.
  • Your boiler and hot water cylinder need to be compatible with a solar thermal system; they are often not compatible with Combi boiler setups as these systems don't require a hot water cylinder.
  • The bigger the hot water cylinder, the more of your solar generated water you'll be able to store and use. Solar compatible cylinders are usually larger in size.

If you think a solar thermal heating system could be the right choice for your home, your next step is to get multiple quotes for installation. You can do this by clicking the link below.

Solar Thermal Heating: Pros, Cons and Costs

Find out if a solar thermal system is the right choice for your home.

Find out more

Solar Thermal with an Immersion Heater

How to use solar thermal with your immersion heater to save energy.

Find out more

Solar Thermal with a Boiler

How to reduce your heating bills with solar thermal AND keep your boiler.

Find out more


Nick Geary

About the author

Nick Geary

Nick has a wide range of experience writing about conventional and renewable heating solutions, and is always increasing his knowledge by researching any new heating technologies on the horizon.

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