Solar Thermal Panels UK - Pros, Cons & Costs

Want to use renewables to meet your home’s hot water needs, all while keeping your bills down?

One such way of approaching this is with the installation of solar thermal panels.

Unlike PV solar panels, solar thermal panels transform solar energy into heat for the purpose of heating water.

So, while PV panels are used to power household appliances, solar thermal panels may be used to heat water for domestic use (e.g. showering).

Either way, though, both can potentially reduce your carbon footprint and reduce your electric bills.

In fact, on average, solar thermal panels can meet approximately 60% of a property’s hot water demand throughout the year.

Ultimately, they’re unlikely to meet 100% of your hot water requirements, but they can potentially save you hundreds of pounds per year.

In this guide, we’ll explain what solar thermal panels are, how they work and explore their costs, features and pros & cons.

Let’s dive in...

PS We offer MCS-certified solar panel installation nationwide. Simply answer these questions, get your fixed price and arrange your free design.

Solar Thermal Panels Key Points: 

• Solar thermal panels use sunlight to heat water for various applications.

• They come in two types: flat plate collectors and evacuated tube collectors.

• They can be used for hot water, space heating, and swimming pool heating.

• Solar thermal panels reduce energy bills and carbon emissions.

• Proper installation, sizing, and maintenance are important.

• Unfortunately, financial incentives like the Renewable Heat Incentive (RHI) are no longer available. 

• Consider factors like roof orientation and shading when installing.

• Consult with qualified installers for professional installation and optimal performance.

What are Solar Thermal Panels?

In short, solar thermal panels are designed to harness the energy of the sun to heat up water for domestic use.

Solar thermal technology comes in two primary forms:

• Flat-plate collectors

• Vacuum tube collectors

In this guide, we are predominantly concerned with flat-plate collectors i.e. solar thermal panels.

However, we’ll touch on vacuum tube collectors toward the end of this article as they should not be overlooked if you are considering a solar thermal installation.

Solar thermal panels/flat-plate collectors are similar in both appearance and structure to regular solar PV panels, which are used to generate electricity for domestic use.

Solar thermal panels have a dark absorbing surface, transparent cover and heat insulation backing layer.

Tubes are also needed to allow water or heating fluid to enter and exit.

While technically you could use solar thermal panels to provide hot water to heat your home, it is best to focus their use on hot water for direct use.

This is, in part, because solar thermal panels simply would not provide anywhere near enough hot water to heat your home.

However, they can generate a substantial percentage of the hot water needed for direct use.

Therefore, it is sensible to use them for hot water outlets only.

Notably, how much of your home’s hot water demand they’ll meet will vary throughout the year, seeing a peak in summer and a significant drop below the average of 60% during the winter.

How Do Solar Thermal Panels Work?

Expanding on the previous paragraph, how a solar thermal panel produces hot water will vary depending on whether it is a direct or indirect system.

Direct vs. Indirect Solar Thermal Panels

In the case of a direct solar thermal system, the panel heats water directly.

However, indirect solar thermal panels heat a fluid which is subsequently sent to the heat exchanger to heat up water outside of the panels.

Inner Workings of Solar Thermal Panels

The absorber used to heat the water or fluid may be made of copper, aluminium, steel or even polymers.

While copper is the costliest of these options, it is a particularly long-lasting conductor.

On the other hand, polymer solar thermal panel collectors are best suited to colder climates.

This is because the materials included (e.g., silicon) are far more resistant to freezing than metallic materials.

A solar thermal system requires a solar-compatible water cylinder in order to do its job.

This cylinder must be of sufficient size to hold approximately two days of hot water at any given time.

If you do not already have one installed, you’ll need to have it fitted along with the solar thermal panels.

Still learning about solar panels? Explore our helpful guides on various topics, including solar panel grants, payback periods, the mechanics of solar energy, determining the number of panels you need, and solar car charging solutions.

Pros of Solar Thermal Panels

As with any renewable technology, solar thermal panels come with a range of advantages and disadvantages.

Let’s start with the upsides...

Can Prove a Great Investment

If you’re looking for a lasting way of reducing your heating bills, solar thermal panels are a great investment.

Depending on the power of the solar thermal panels you purchase, the hot water demand of your household and various additional factors, a solar thermal panel setup will likely cut your annual hot water bill by 50-70%.

These savings are based on current energy prices (as of July 2024).

Ultimately, the larger your home is and the more hot water you use, the more solar thermal panels should take off your heating bills.

Eco-friendly Option

Of course, as a renewable source of energy, solar thermal panels are better for the environment.

Moreover, as a non-pollutant, solar thermal panels can reduce your carbon footprint. While solar thermal panels require some running costs, these are often minimal.

Low Maintenance Solution

Solar thermal panels are also relatively low maintenance. While a boiler needs to be serviced annually, a solar thermal setup should only require servicing every three to five years.

With that said, if you do notice any issues, they should be serviced sooner. Solar thermal panels tend to have a life expectancy of 20-25 years.

Cons of Solar Thermal Panels

While there are plenty of advantages to using solar thermal panels, they also come with many downsides.

Expensive Installation

The main disadvantage is that solar thermal panels do not come cheap.

In fact, on average, it tends to cost somewhere in the region of £3,000 to £5,000 to have a solar thermal panel setup installed.

Won’t Meet Full Demand

Beyond that, solar thermal panels do not generally meet a property’s entire hot water needs with the average installation meeting about 60% of a property’s yearly hot water needs.

Therefore, you’ll still need to use a boiler, immersion heater or another setup for this purpose.

Combi Boilers Are Often Incompatible with Solar Thermal Panels

Whatever type of boiler you have (i.e., combi, regular or system boiler), it’s important to ensure that the boiler you have installed (or the replacement boiler you plan to have fitted) is compatible with solar thermal panels.

While a very popular option, many combi boilers are not compatible with solar thermal technology.

This is because combi boilers have water fed directly through the mains, allowing them to produce hot water on demand.

If you have a regular boiler and ultimately do opt for a solar thermal installation, additional infrastructure may be needed. This will depend on the type of regular boiler you have.

Again, whether you have a combi, regular or system boiler, be sure that yours is compatible with a solar thermal panel installation before proceeding.

Not All Properties Suit a Solar Thermal Installation

Lastly, a solar thermal array will not be suitable for all properties.

With that said, if they are positioned anywhere from southeast to southwest, they can still be worth the investment.

If the back roof of your home is north-facing, then it would be a no-go.

Of course, if that is the case, you may want to consider fitting the solar thermal panels to the front roof of your property.

For many, their gut reaction would be to oppose the idea right off the bat of front roof solar panels.

However, it is worth considering, especially given that solar panel use is becoming increasingly popular and not seen as an eyesore by as many people as you might expect.

Cost of Solar Thermal Panels

Firstly, it’s important to note that solar thermal panels must be installed by an MCS-certified installer.

A heating engineer may also be needed if you wish to have a solar-compatible hot water cylinder fitted.

In most cases, a solar thermal array should offer one square metre of panel for every person living on the property.

For instance, a house of four should have about 4m² of solar thermal panels.

Since the average solar thermal panel is 2m², two solar thermal panel units should suffice for a family of four.

Average Cost of Installation

For an average household, a solar thermal system will likely cost somewhere in the region of £3,000 to £5,000.

For small properties with a relatively low hot water demand, expect a total cost of under £3,000.

If you have a large property with a relatively high demand for hot water, it’s likely to set you back around £7,000 or more to have solar thermal panels installed.

Then, if a new solar-compatible hot water cylinder is required, expect to see a further £600 to £1,000 added to your overall bill.

Again, to have your hot water cylinder replaced, you’d need a heating engineer for this task.

Factors Impacting the Cost 

How much your final bill will come to will ultimately depend on a wide range of factors.

Aside from the factors already touched on, the cost of a solar thermal array installation can vary depending on:

• The cost of labour in your area

• The type and quality of solar thermal panels used

• Ease of access to the workspace

• The complexity of the installation

• The type/quality of the new hot water cylinder (if applicable)

Finding the Right Professional(s) for the Job

When it comes to hiring an MCS-certified installer for a solar thermal system setup or/and finding a heating engineer to fit a hot water cylinder, it’s important not to rush the process.

We recommend securing quotes from at least three MCS-certified installers/companies with MCS certified installers before making your decision.

The same logic applies if looking for a heating engineer to install a hot water cylinder. This may or may not be possible depending on where you live, but it’s worth a try.

By having at least three quotes to compare, you’ll be able to determine which of the three offers the best value for money.

By doing so, you might end up saving a few bobs in comparison with just choosing the first professional/company you find.

To figure out who offers the best value for money in any given case, we advise considering the quote they offer, their previous experience and any online reviews/ratings they might have.

Best Solar Thermal Panels on the Market

If you are seriously thinking about having a solar thermal system installed, you’ll want to know what the best options are on the market.

To find the right solar thermal panels for you, be sure to take into consideration your budget and key priorities.

Then narrow down your list to the panels that you consider the best fits.

Viessmann Vitosol 100-FM

• Efficiency: 80.3%

• Product Warranty: 5 years

• Average Cost: £3,000 to £4,600 for two panels with an area of approx. 4m²

Arguably the best solar thermal panel (that utilises flat plate technology as opposed to vacuum tube collectors) is the Vitosol 100-FM.

Along with being a powerhouse in the boiler manufacturing market, Viessmann is now bringing its impeccable German engineering to the field of solar thermal technology.

The Vitosol 100-FM is not the only solar thermal panel produced by Viessmann but we believe it offers the best value for money.

With a superb energy engineering rating of 80.3%, the Vitosol 100-FM can slash household heating bills by as much as 30%.

The Viessmann Vitosol 100-FM features a ThermProtect absorber layer which helps to ensure that the panel(s) will not overheat.

This flat plate collector may be installed using either of the following set-ups; flat roof, wall mounted, above roof and roof integrated.

If you are willing to spend more, however, you may want to consider the Vitosol 200-FM.

Worcester Bosch Greenskies Solar-Lifestyle

• Efficiency: 76.6%

• Product Warranty: 10 years

• Average Cost: N/A

Worcester Bosch, like Viessmann, has plenty of name recognition when it comes to boilers.

However, they too have begun to establish a reputation for manufacturing top-quality solar thermal panels.

In our view, the best solar thermal flat plate collector offered by Worcester Bosch is their Greenskies Solar-Lifestyle.

The Worcester Bosch Greenskies Solar Lifestyle may be added atop a roof, within a roof or on a wall.

There is a vertical and horizontal version of this product.

The stats given above are applicable to the vertical version. The horizontal version differs in a few ways (e.g., the energy efficiency of 75.6% rather than 76.6%).

Other Notable Solar Thermal Panels

Aside from the two best options listed above, you might also want to consider:

• Viessmann Vitosol 200-FM

• Viessmann Vitosol 300-FM

• Worcester Bosch Greenskies Lito

What about Vacuum Tube Collectors?

Vacuum tube collectors are simply another design/structure that can be used to create a solar thermal system.

Unlike flat plate collectors, vacuum tube collectors consist of various rows of parallel glass tubes.

These transparent tubes connect to a head pipe, enabling fluid to enter the system and absorb the heat produced by the tubes. This fluid then travels back into the property to heat up water.

Benefits of Opting for Either Type of Solar Thermal System

Flat Plate Collectors:

• Usually somewhat more affordable

• Many households will prefer these due to their more familiar appearance and the fact they can be integrated into the roof

Evacuated Tube Collectors:

• Tend to be more energy efficient

• Due to design differences, evacuated tube collectors are more flexible in terms of where they can be installed and are expected to perform well

• Better suited to especially cold winters

If you are also open to having vacuum tube collectors installed, we especially recommend considering the Solar UK LaZer 2.

This product is arguably superior to all of the best solar thermal panels listed in the previous section, although not by a huge margin.

How Much Can Solar Thermal Panels Save You?

According to the Energy Saving Trust, the average UK household spends about £230 per year on hot water.

Based on this, and considering solar thermal panels can, on average, meet 60% of a property’s hot water demand, the average UK home stands to gain savings of about £130 to £140 annually.

Of course, how much you’ll actually save each year will depend on your current heating source and heating bills, the number of solar thermal panels you install, and where you live in the UK.

After all, some parts of the UK see more sunlight than others.

Can you get free or subsidised solar panels in the UK? 

Potentially yes, you can apply for funding and may be eligible for help with the costs of a solar panel installation via the ECO4 scheme. 

Explore what solar panel grants and funding are currently available in our comprehensive solar grant guide here. 

Next Steps For Your Solar Journey:

When planning to install solar panels for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:

• How much do solar panels cost? 

• Are solar panels worth it for your home? 

• Is your roof suitable for solar panels? 

• What are the best solar panels available? 

• Is battery storage worth it? 

To dive deeper into these topics, head over to our advice section, check out our YouTube channel for informative videos, or read a customer case study to see how others have benefited from their solar installation. 

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