Solar thermal panels

Solar thermal panels convert daylight into heat energy, efficiently heating your home’s water and living spaces. Complementing electricity-generating solar photovoltaic panels, they can reduce your energy bill by £130 to £235 annually and meet up to 90 per cent of your hot water needs in summer, while cutting CO2 emissions by up to 930kg per year. Environmentally, it’s a smart choice.

Our experts explore how solar water heating works, its benefits, and costs, which range from £3,000 to £8,000. We’ll also compare savings against traditional heating methods like oil, coal, and electricity to help you determine if a solar water heating system is right for your home in 2024.

Solar thermal panels (also known as solar thermal collectors) are devices that capture sunlight and convert it to energy to heat your home’s water and interior spaces. Although direct sunlight produces the best results, they can still generate energy from regular daylight.

Unlike the best solar panels, which convert daylight directly into electricity to meet your home’s lighting and power needs, solar thermal panels turn daylight into heat. This heat is used to warm the water in your home’s hot water cylinder or thermal store, which you can then use for showering, hand washing and bathing. Solar thermal panels can also be used for home and swimming pool heating.

Research suggests that solar thermal panels can save you around 10 per cent on your energy bills and provide an average of around 60 per cent of your domestic hot water requirements annually. Owing to the sun’s varying output throughout the year, though, domestic arrays are unlikely to provide the entirety of your home’s hot water needs – you’ll still need an immersion heater or conventional boiler to make up the shortfall.

Typically, solar thermal panels consist of a series of tubes or panels, which contain a heat-absorbing material covered by a transparent plastic or glass cover. These are mounted on your home’s roof, where there’s (ideally) optimal sun exposure.

When daylight strikes the absorber material, it heats up. This transfers the heat energy to the fluid – usually a mix of water and antifreeze – circulating through the tubes or panels, converting the infrared portion of the light into usable heat.

This heat is then transferred – either with pumps in an active system or through simple gravity in a passive one – through pipes and tubes to your hot water tank. It can be used straight away or stored in your home’s thermal store for later use, whereupon it’s channelled through your home’s plumbing or heating system to warm your water and home.

Some solar thermal systems may include extra features, such as controls and sensors to regulate the flow of fluid, keep tabs on water temperatures and optimise the capture and use of energy to increase the system’s energy-efficiency and cost-effectiveness.

You can also invest in a thermal battery. This emerging technology works similarly to the way a solar battery stores excess electricity for use during times when power is more expensive, saving up the residual heat energy generated by your solar thermal panels to warm your home’s water on demand.

Solar thermal panels come with plenty of benefits for your UK home – not to mention the cost of your monthly electricity bill!

Let’s explore the drawcards of a solar water heating system in more detail.

It provides a consistent supply of hot water throughout the year

While solar thermal panels won’t provide for your home’s entire water- and space-heating needs, these clever devices certainly pull their fair share of the weight.

According to Energy Saving Trust, solar thermal panels will account for 25 per cent of your property’s hot water requirements in winter and an impressive 90 per cent in summer. Overall, this is around 60 per cent of your thermal needs throughout the year.

It saves you money on your energy bills

By bolstering your regular hot water system with the sun’s energy, solar thermal panels can save you money on your energy bills by as much as 10 per cent, according to some estimates. This means that while you’ll have to pay an initial installation cost, you’ll eventually recoup that investment through incremental savings.

Scroll down to learn more about how much solar thermal panels will cost you, and dive into the table below for an idea as to how much they can save you compared with your existing hot water system in 2024.

What’s more, solar thermal panels are easy – and affordable – to maintain, with relatively low operating costs helping to offset your original outlay.

It’s a clean, guilt-free source of energy

Since solar thermal panels draw on an abundant, sustainable resource – the sun’s energy – they’re a clean, green source of renewable energy. Unlike oil-fired water heaters (or ones that rely on propane, natural gas or coal) solar thermal panels don’t contribute to climate change by emitting carbon dioxide and other harmful greenhouse gases.

This means that solar thermal panels are an important part of your duties to the environment. For more ways you can help the planet, explore our guide on how to be eco-friendly.

You can also explore the below table, again courtesy of Energy Saving Trust, to find out just how much your switch to solar thermal panels could save the world in carbon dioxide emissions compared with your home’s existing hot water system.

It’s more energy-efficient than solar PV

When it comes to heating water, solar thermal panels beat traditional solar panels for energy-efficiency. Because solar thermal panels directly convert sunlight into heat energy – without the need for the intermediate conversion process required with solar PV, in which the generated DC is transmuted into useable AC – they can be up to 70 per cent more efficient.

Solar thermal panels are also less complex and more space-efficient than their PV counterparts. These factors combined make solar thermal panels a more accessible solution for homeowners looking to dip their toes into the world of renewable energy.

In the UK, a solar water heating system will cost you anywhere between £3,000 and £8,000 for a typical three-bedroom house, at an average cost of around £4,500. This typically buys you a 5m2 thermal collector roof area and a cylinder with a 250l capacity.

This covers installation and all the components you’ll need, including the control panel, pipes, hot water tank and the solar panels themselves. What it doesn’t include (at least up until 31 March 2027) is VAT, with solar thermal panels for residential properties exempt.

How much you pay for your solar hot water panels will also depend on the provider, the size of the setup and the type of system. For example, costs vary depending on whether the system relies on active or passive technology and whether there are any additional features included, such as fluid-regulating controls and sensors. It’ll also depend on whether you opt for a professional system and installation or go it alone with a DIY kit, which you can purchase for around £1,750.

The UK has a rich history of grants and incentives for solar thermal panels, with the Low Carbon Buildings Programme giving way to the Renewable Heat Premium Payment (RHPP), which then paved the way for solar water heating grants such as the now-expired Green Homes Grant and the Renewable Heat Incentive (RHI).

However, the RHI closed to new applications on 31 March 2022 – so what’s replaced it?

The answer, right now, is not much; as of August 2024, the RHI doesn’t have a direct replacement. However, residents of Scotland can take advantage of the Home Energy Scotland Grant and Loan scheme – it’s not a grant per se, but does offer a £5,000 loan towards installing a solar water heating system.

There are other UK grants available to aid with the transition to renewable domestic technologies, such as the ECO4 and Smart Export Guarantee (SEG), but these only apply to solar PV rather than solar thermal panels. You can read more about these in The Independent Advisor’s guide to the solar panel grants you need to know about in 2024.

Depending on your existing hot water system, solar thermal panels could save you between £130 and £235 per year. Given that a solar water heating system costs around £4,500 on average, does that represent good value? And how long will it take to break even?

If your home currently relies on electricity, after switching to a solar water heating system, it will take you less than two decades to recoup your investment. With coal, it’s a quarter of a century, while oil and LPG are more like a third of a century. If you’re switching to solar from a gas-powered hot water solution, the breakeven point is almost four decades.

Of course, we’re talking here about the financial break-even point, not the ethical one. And there’s a lot to be said for the benefits of a clear climate conscience. Make the switch from a coal burner, for example, and in the 25 years it’ll take you to recoup your initial financial outlay, you’ll also have been responsible for preventing 22,320kg of carbon dioxide emissions from making their way into our environment.

The calculations here also don’t include the potential savings from yet-to-be-announced government grants. Without gazing too deeply into our crystal balls, these have been a regular feature of policy in the last few years – so it’d be a shock if there weren’t more financial incentives announced for UK homeowners to install and utilise sustainably sourced hot water.

Installing solar thermal panels is an excellent way of guaranteeing a steady supply of sustainable, sun-sourced energy throughout the year. But it won’t be suitable for all homes.

Take a look at our checklist below to find out if your property is well placed to accommodate a solar water heating system and, if not, what you need to do to prepare it for one.

The right roof

Although your solar thermal panels don’t always have to be placed on your roof – some are ground- or wall-mounted – it’s often the optimal place for them.

But not all roofs are created equal. To facilitate solar thermal panels, yours will need:

• Access to daylight: your roof must be have access to daylight without neighbouring buildings or trees blocking it off
• Sufficient surface area: depending on the size, a typical rooftop-mounted solar thermal system will require between 16m2 and 28m2 of space
• Positional perfection: the ideal angle for solar thermal panels in the UK is between 20 and 50 degrees with a south-facing orientation to maximise sunlight hours

A functional boiler and hot water cylinder

Solar thermal panels don’t work in isolation but as part of a trio that also includes a hot water cylinder and a boiler. Your hot water cylinder acts as a reservoir for the heated water your solar thermal system produces, while your boiler acts as a backup heat source, particularly in winter when it’ll take over from solar as your main source of hot water.

As a result, you’ll need to ensure your boiler is in working order and that it’s compatible with solar thermal panels. Fortunately, most conventional boilers in UK homes today are, although there are some exceptions.

The following boilers, for example, may be incompatible with a solar setup:

• Combination (combi) boilers: these provide space heating and hot water from a single unit and typically have only a small internal hot water tank. This limits their ability to store the preheated water your solar thermal panels generate
• Electric boilers: while it’s possible to integrate solar thermal panels into an electric boiler, these tend to have limited hot-water storage capacity, and the overall system isn’t as energy-efficient as systems with boilers fuelled by natural gas, propane or oil
• Old or inefficient boilers: if your boiler requires regular maintenance or is generally inefficient, it will negate many of the energy-saving benefits of your solar setup

Planning permission

Unlike domestic solar PV panels (which come with more stringent requirements around planning permission), solar thermal panels generally don’t require approval from your local council. That’s provided they’re for residential use and your property isn’t listed or part of a World Heritage site. If it is, your panels must not be visible from the road.

Your solar thermal panels must also not:

• Be installed on any part of your property’s external walls if the building contains a flat
• Be situated within a metre from the edge of the roof
• Protrude more than a metre above the plane of the roof
• Project higher than the roof’s highest point (except for the chimney)

If your property meets these conditions, it’s unlikely you’ll need planning permission for your solar thermal panels. But it’s good practice to contact your local council to double-check.

When it’s time to install your solar thermal panels, we recommend scouring the market to compare quotes. If that sounds taxing, simply take 60 seconds to fill out our short form with some details about your solar water heating system needs and we’ll pair you with free, tailored quotes from the UK’s leading suppliers.

Of course, not all solar thermal panel installers are worth their salt. It’s the same deal as with solar panel costs: some suppliers will include installation costs in the quote, while other, less reputable, ones may count setup costs as a separate fee (often hidden in reams of small print).

It’s also worth researching the market for local, regional solar thermal panel installers. They may not be as prominent as the large, national suppliers hogging the Google search results and dominating the advertising space, but according to research by the National Renewable Energy Laboratory, these “smaller fish” gave customers a lower quote 70 per cent of the time compared with their bigger competitors. And these quotes were around 10 per cent less on average.

Another thing to look for before you pick a supplier is Microgeneration Certification Scheme (MCS) accreditation. Essentially, this is a certification solar thermal and PV solar panel installers receive that proves they and their products are up to the rigorous standards required by the industry. MCS certification isn’t mandatory by law, but it’s absolutely recommended.

Finally, there’s the question on the lips of all self-confessed DIYers everywhere: can you install solar thermal panels yourself? The answer is yes, you can – and a DIY kit will cost you in the ballpark of £1,750. This is far less than it would cost you with an accredited company, but the DIY approach does come with drawbacks.

For one, these kits don’t come with MCS certification. Previously, MCS-approved solar thermal panels have been required to claim access to now-expired government incentives, such as RHPP and RHI. While this isn’t too much of an issue right now given that there are no active government grants for solar water heating systems as of 2024, any future incentives will almost certainly require MCS certification. And, given the financial benefits these incentives will offer, it makes sense to spend a little more now for professional installation, then reap the rewards down the line.

The question “are solar thermal panels worth it?” is a nuanced one because it depends on your response to another question: “what matters to you?”

If your answer is money, and you’re motivated purely by the cost savings renewable technology might offer, then no – solar thermal panels aren’t worth it. Even accounting for the cost of an average solar water heating system (rather than one at the upper end of the price spectrum), it will still take you between 19 and 38 years to recoup the initial cost.

If you nurture a less short-term, money-oriented view and choose instead to focus on the environmental benefits of solar thermal panels, the picture looks rosier. Every decade, your solar water heating system will prevent between 3,100kg and 9,300kg of CO2 emissions that would have otherwise entered the atmosphere, exacerbating the already perilous, precipitous picture for the planet.

Unknowns still exist, of course. At this stage, with solar thermal panels still a relatively lesser-known technology – having failed to grip the public imagination in the same way solar PV panels now have – it’s not clear which direction prices will fluctuate.

If the price of solar PV panels is anything to go by, though, solar water heating system prices may be set to become more affordable over the next decade.

According to the 2023 edition of Berkeley Lab’s Tracking the Sun report, the installation price of residential solar PV panels has dropped by 23 per cent over the last decade as the technology becomes both more affordable and more prominent in public discourse. Widen the scope back to 2000, and solar PV modules are an incredible 90 per cent cheaper now than they were then.

It bodes well for the price of solar thermal panels going forward – less so for anyone looking to save money by getting in on the ground floor of this emerging technology. As we’ve already discussed, though, adopting renewable technology for your home isn’t just about saving a pound or two – it’s also about doing your bit for the planet. And that certainly can’t wait.