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Solar Thermal Heating: Pros, Cons and Costs

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

Solar thermal heating systems capture the free, renewable energy from the sun and use it to heat water in your home.

These systems give homeowners 70% of their hot water for free. Taking the strain off their boiler or immersion heater.

But is a solar thermal system right for your home? We've taken a closer look at the pros, cons and costs of solar thermal.

Pros of solar thermal heating

Reduced heating bills

On average, a solar thermal heating system is capable of producing between 40 – 70% of the hot water needed by a family of 4 in a year. By heating water with free solar energy rather than your boiler you'll need to use your boiler or immersion heater significantly less and won't need to pay for as much fuel. And, while you're likely to still need your boiler in winter, the solar thermal panels will still generate some heat, raising the temperature of the water so the boiler doesn't need to work as hard.

Lower carbon footprint

Reducing how often you need to use your boiler will not only reduce your heating bills, but also cut your home's carbon emissions as you'll be burning less fossil fuels, so you can do your bit to help the environment.

Almost no running costs

Once the system is up and running there are almost no running costs to budget for. You will need a professional to check over the system every few years but other than that it will run on free energy.

Low maintenance

Solar thermal systems only require professional servicing every 3-5 years. They tend to covered by manufacturer warranties between 5-10 years. In addition, the solar thermal system will reduce the strain your boiler as it won't be working as hard so this should lengthen its life with less likelihood of repairs.

Cons of solar thermal heating

Not a complete heating system

For most homes, a solar thermal system won't be able to provide the entire hot water supply. You will still need a boiler or immersion heater to boost the supply on cloudy days and meet the higher demand for heating in winter. A solar thermal system will also not power electric showers or cold-fill washing machines / dishwashers.

High upfront cost

A stumbling block for some homeowners can be the upfront cost of installing a solar thermal system of between £3,000 – £5,000 on average.

Specific installation needs

To work at optimum efficiency solar thermal panels need to be installed on a roof facing due south at a 20-50 degree angle from horizontal, although they can work effectively when positioned between south east and south west. In some cases it's possible to install them on the ground or on a wall but any shade will reduce their effectiveness. You will also need to have or install a solar compatible water cylinder which is large enough to hold around 2 days of hot water.

Not suitable for all heating systems

Solar thermal systems are often not compatible with Combi boilers as they are fed water directly from the mains and heat water demand; you will need to check with the manufacturer if your Combi boiler will water which has been pre-heated by solar thermal. If you have a Regular heating system which is gravity fed you will need an extra valve or pump so the system can work effectively in winter when the heating is running at the same time.

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Solar thermal installation costs

To install a solar thermal system tends to cost between £3,000 – £5,000 for an average home, i.e. a family of four. This is of course an estimate and in some cases larger systems may be needed if the demand for hot water is higher; in these instances costs could rise to £7,000.

Industry recommendations suggest that you will need around 1m² of panel per person living in the home. The installation cost will also depend on how complex the process and how easily it integrates into your existing heating system.

If your hot water cylinder is not solar compatible you may also need to invest in a new one which could cost between £600 – £1,000 on average.

However, when calculating the likely upfront costs of solar thermal it's important to keep in mind that it's highly likely you'll be saving money on cheaper heating bills. The Energy Saving Trust estimates that solar thermal panels could save you £50 a year if you have a gas boiler, £55 if you have an oil boiler, £65 if you use coal, £80 if you have an electric boiler and £95 if you use LPG (liquid petroleum gas).

Get free solar quotes

Ready to power your home with solar?

Then visit our sister website Solar Guide today to get free quotes from solar installers near you.

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What is a Solar Thermal Heating System?

Solar thermal means using free energy from the sun to heat your home's water.

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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