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Solar Thermal vs Heat Pumps

Solar Thermal vs Heat Pumps

Finding a suitable renewable heating system often comes down to 2 options: solar thermal vs heat pumps. Solar thermal panels collect heat from the sun while heat pumps extract heat from the air or ground.

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.

Between September 2020 and March 2021, you could be eligible to receive government funding for up to two-thirds of the cost of installing a renewable heating system through the Green Homes Grant.

Solar thermal vs heat pumps: How do they work?

As renewable heating systems solar thermal panels and heat pumps convert energy from renewable sources 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 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 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.

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 of the strain off your boiler

Air source heat pump benefits

  • Perform to highly efficient levels of 300-400%
  • Air-to-air heat pumps can provide cooling during the warmer months
  • Need very little maintenance during their lifetime
  • Able to continue generating heat in temperatures as low as -20°C to -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 in the way of maintenance

Cost of solar thermal and heat pumps

Compared to conventional 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

The initial investment doesn’t give the whole picture.

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.

Solar thermal vs heat pumps: How much could I save?

While the upfront costs of these renewable heating systems is often much higher than conventional heating systems – such as boilers – you will be saving money in the long run. This is because you’ll be generating your own renewable energy rather than relying on an energy supplier.

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 look over them every few years, you can leave them to do their job.

Once installed, a solar thermal heating system has the potential to deliver between 40 and 70% of your demand for hot water over the course of a year.

According to the Energy Saving Trust, 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

Unlike solar thermal systems, heat pumps require electricity to operate.This is likely to lead to an increase in how much you pay for electricity. However, unlike solar thermal panels, a heat pump can continue generating heat once the sun has set.

Current Heating System Potential Savings with an Air Source Heat Pump Potential Savings with a Ground Source Heat Pump
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

As you can see from the table above, if you have a recently installed A-rated gas or oil boiler then your energy bills could actually increase. This is because of the electricity required for the heat pump to operate.

To keep heat pump electricity usage costs to a minimum, you could generate your own renewable electricity with a solar photovoltaic (PV) system. Rather than converting solar energy into central heating and hot water, solar PV generates renewable electricity.

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.

Renewable Heat Incentive

Heating your home and hot water with energy generated by a renewable heating system can entitle you to payments through the Renewable Heat Incentive (RHI). RHI payments are made quarterly and you will continue to receive them for 7 years. The tariffs are reviewed on a quarterly basis so the tariffs at the time of submitting your application will be the amount you receive.

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.

Renewable Heating System Renewable Heat Incentive Tariff (p/kWh)
Air Source Heat Pump 10.85
Ground Source Heat Pump 21.16
Solar Thermal 21.36

Tariffs based on applications submitted between 1 July 2020 and 31 September 2020.

Solar thermal and heat pump considerations

As renewable heating systems, 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 conventional boilers. To counteract this, they’re best suited to well insulated homes with large radiators or underfloor heating. The larger surface area of the heating systems allows for heat to spread around the room, despite the lower temperatures.

Solar thermal heating system considerations

  • Not a complete replacement for your current heating system as they’re only able to generate heat during daylight hours
  • For most efficient performance 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

  • There will also be some operating noise although manufacturers work to make their systems as quiet as possible
  • If your main priority is lower energy bills then it’s not worth replacing a new modern A-rated gas or oil boiler as you could actually see your energy bills rise
  • Lose efficiency during the winter months when temperatures drop
  • Some outdoor space is essential for the installation of the heat pump unit
  • A retrofit installation can be challenging
  • An air-to-water heat pump must be installed as part of a heating system that also includes a hot water storage 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 as opposed to vertically)
  • The installation can be disruptive and take between 2 and 3 days
  • Retrofit installation may not always be possible
  • Requires a supply of electricity to operate

Air source vs ground source heat pumps

When it comes to choosing between air source and ground source heat pumps, an air source heat pump is likely to be the most suitable. This is because they take up less space and aren’t as disruptive to have installed.

Both heat pumps require outdoor space but the installation of a ground source heat pump requires pipes being buried underground. Not only does this mean plenty of space is essential, your property will also need to be able to accommodate the necessary machinery too.

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

Solar thermal vs heat pumps: Which is best suited to your home?

Renewable heating systems are growing in popularity as homeowners become more conscious of their impact on the environment. 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 for your property. This is because they must be installed as part of a heating system which includes 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.

To find out if your home is suited to a renewable heating system you should seek the opinion of qualified installers.

Get free installation quotes

When you’ve decided which renewable heating system is best suited to your home, it’s time to get quotes from local installers. We highly recommend comparing multiple quotes for the installation as it will greatly increase your chances of finding the most competitive price.

You can get free quotes from local heat pump installers right here on Boiler Guide. All you need to do is complete our online form – which should only take a few minutes. Once you’ve finished, we’ll get to work matching you with installers in your area qualified to complete the work.

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

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