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Solar Thermal vs Heat Pumps

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

Solar Thermal vs Heat Pumps

Comparing solar thermal vs heat pumps will help you find the right renewable heating system for your home.

Solar thermal panels absorb heat from the sun while heat pumps take heat from the air (air source) or underground (ground source). Both offer many benefits, including the potential to lower your heating bills. However, one is likely to be more suitable for your home than the other.

In this article we'll help you to decide between solar thermal vs heat pumps.

How solar thermal and heat pumps work

As renewable heating systems solar thermal panels and heat pumps turn renewable energy into heat.

Solar thermal heating systems extract heat from the sun while heat pumps take heat from either the air or the ground. This heat can then be used to provide central heating and domestic hot water to the property.

Solar thermal panels

Solar thermal panels are installed onto a roof where the heat from the sun warms a liquid in the collectors. This liquid is then circulated round a wet central heating system or into an immersion heater within a hot water cylinder which heats the domestic hot water.

Air source heat pumps

Air source heat pump systems include a fan that's installed outside which draws in the outdoor air. This air is then heated further by a heat exchanger. Air source heat pumps are available as air-to-water or air-to-air systems. An air-to-water heat pump produces hot water for a wet central heating system and hot water storage cylinder. Meanwhile, air-to-air heat pumps are similar to air conditioning systems, circulating hot air around the home via fans. They can even cool your home down during the summer.

Ground source heat pumps

Rather than extracting heat from the air, ground source heat pumps take heat from under the ground where temperatures sit at a consistent 10°C to 15°C all year round. To collect this heat, an underground pipe network needs to be installed in a garden area. This can be done either horizontally (requires more space) or vertically.

A refrigerant liquid is circulated through the underground pipes which is warmed by the underground temperatures. The liquid then travels round to the heat exchanger where it's heated further before it warms up the central heating system.

Benefits of solar thermal and heat pumps

No matter whether you decide to have solar thermal panels or a heat pump, you'll benefit in a number of ways:

  • Reduced carbon footprint
  • Less reliance on your energy supplier
  • Potentially lower heating bills
  • May increase the value of your property
  • Much safer than gas and oil boilers as no fuel is burned
  • Renewable Heat Incentive (RHI) payments

There are more benefits to heating your home with renewables but they will depend on the type of system you have installed.

Solar thermal benefits

  • No running costs
  • Very low maintenance
  • Help to take some strain off your boiler – reducing the risk of a breakdown

Air source heat pump benefits

  • Highly efficient performance of 300-400%
  • Air-to-air heat pumps can cool during the warmer months
  • Need very little maintenance during their lifetime
  • Able to generate heat in temperatures as low as -25°C

Ground source heat pump benefits

  • Underground temperatures remain at a consistent temperature all year-round (10°C to 15°C)
  • Need very little maintenance

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Cost of solar thermal and heat pumps

Compared to gas and oil boilers, renewable heating systems have a higher price. Particularly ground source heat pumps.

Renewable Heating System Potential Cost
Solar Thermal £3,000 – £7,000
Air Source Heat Pump £4,000 – £11,000
Ground Source Heat Pump £8,000 – £12,000

That initial investment doesn't give the whole picture though.

A renewable heating system will help to reduce the reliance you have on your energy supplier. And, as a result, you could see a reduction in your energy bills.

So, over time, the savings you make on your energy bills, combined with RHI payments, could potentially see you see a return on your investment.

How much could I save?

Renewable heating systems are pretty expensive. Especially when compared to gas boilers. But once you’ve made that initial investment, you could be saving money in the long run.

The running costs of a solar water heating system are next to nothing. All they need to operate is heat from the sun. And other than hiring a professional to service them every few years, you can leave them to do their job.

Once installed, a solar thermal heating system has the potential to deliver 40-70% of your home’s hot water each year.

You could be making the following savings depending on your current heating system.

Current heating system Potential annual saving
Gas boiler £50
Oil boiler £55
Electric boiler £80
LPG boiler £95

Source: The Energy Saving Trust

Unlike solar thermal systems, heat pumps need electricity. This will see you paying more for electricity. However, unlike solar thermal panels, a heat pump will continue heat the home after sunset.

Current heating system Potential savings with air source Potential savings with ground source
G-rated gas boiler £400-£465 £505-£580
A-rated gas boiler Increase £35-£55 £65
Old G-rated oil boiler £460-£545 £900-£1,100
New A-rated oil boiler Increase £45-£55 £560-£665
Coal £425-£525 £525-£645

If you have a new A-rated gas or oil boiler your energy bills could increase with a heat pump. Mainly because of the increased electricity costs. So you’re better off holding onto your boiler and considering a heat pump after 8-10 years.

There is a way to keep your electricity costs down, even with a heat pump. And that’s by turning to a solar PV system.

Solar PV panels turn solar energy into free renewable electrity for your home.

This renewable electricity can be used to power the electrical appliances around your home. And, as heat pumps need electricity to work, solar PV panels can power a heat pump. This would help to greatly reduce your electricity costs.

Earn money with the Renewable Heat Incentive

Turning to renewable heating can earn you money through the Renewable Heat Incentive (RHI).

RHI payments are based on how much heat your solar thermal panels or heat pump generates (although there is a cap). Payments are made each quarter and you’ll receive them for 7 years.

Between solar thermal and heat pumps, it's solar thermal panels that currently have the highest tariff. Of the different types of heat pump, ground source comes out on top over air source.

Heating system RHI tariff (p/kWh)
Air source heat pump 10.92
Ground source heat pump 21.29
Solar thermal 21.49

RHI tariffs are adjusted every quarter. The above are based on applications submitted since 1 April 2021.

The RHI is due to close to new applications from April 2022. Taking its place will be the Clean Heat Grant.

Solar thermal and heat pump considerations

Solar thermal panels and heat pumps can benefit your home in many ways. However, there are some important considerations to make before having either system installed.

For example, renewable heating systems don't heat water to the same high temperature as gas or oil boilers. This means they’re best suited to well insulated homes with large radiators or underfloor heating. The larger surface area allows heat to spread around the room, despite the lower temperatures.

Solar thermal heating system considerations

  • Not a complete replacement for your current heating system
  • The panels need to be installed onto a south-facing roof at a 20-50 degree angle
  • Only suitable for installation alongside a heating system that includes a hot water cylinder (this rules out solar thermal if you have a combi boiler)

Air source heat pump considerations

  • Some noise as they heat the home but manufacturers aim to make them as quiet as possible
  • May increase energy bills of homes with a new A-rated gas or oil boiler
  • Lose efficiency during the winter months
  • Some outdoor space is needed
  • An air-to-water heat pump must be installed with a cylinder
  • Powered by electricity which could increase your energy bills

Ground source heat pump considerations

  • Outdoor space is essential (moreso if the underground pipes are being installed horizontally)
  • The installation can be disruptive and take between 2-3 days
  • Retrofit installation isn’t always be possible
  • Needs a supply of electricity

Air source vs Ground source

An air source heat pump is the best option for most homes. They take up less space and aren't as disruptive to install.

Both heat pumps need outdoor space. But ground source installation means burying pipes underground. Not only does this mean plenty of space is essential, various machinery will need access to your property too.

Get help making a decision on which heat pump is best suited to your home in Air Source vs Ground Source Heating Systems.

Which is right for your home?

Renewable heating systems have grown in popularity. Spurred on by homeowners becoming more conscious of their impact on the planet. Solar thermal panels and heat pumps are both highly efficient heating systems that don't emit carbon into the atmosphere.

In all likelihood, one of these renewable heating systems will be more suitable to your home than the other.

If you have a combi boiler – as the majority of UK homes do – then a solar thermal heating system or air-to-water heat pump won't be suitable. This is because they must be installed alongside a hot water cylinder. Properties with a system or regular boiler will have a hot water cylinder but you must ensure it's solar compatible. Otherwise it will need to be replaced.

A major benefit of solar thermal panels is that the installation isn't overly disruptive. Heat pumps, on the other hand, can be challenging to install. Ground source more so than air source.

The best thing to do is ask a qualified installer. And you can get free quotes from heat pump installers near you today. It only takes a minute to complete our online form and up to 3 installers will be in touch to arrange a quote. By comparing more than a single quote, you can be confident that you’re getting a competitive price.

To get free solar thermal quotes, please visit our sister website Solar Guide.

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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