Hot water accounts for around 12% of the average household energy bill, so it’s no surprise that residents across Lancashire are looking for smarter, more sustainable ways to heat the water in their homes. One option that’s been quietly delivering results for decades is solar thermal water heating – a technology that uses the sun’s energy to provide hot water for everyday use.
If you’re thinking of installing solar thermal, or already have a system and want to understand it better, this blog answers the most common questions.
What Is Solar Thermal?
Solar thermal systems – sometimes called solar water heating – use the sun’s energy to heat a special fluid that transfers warmth into a hot water cylinder inside your home. They don’t generate electricity like solar PV panels; instead, they’re designed to provide hot water for showers, baths, and taps.
The system typically includes collectors on your roof (or another sunny location), a pump, a controller, and a hot water cylinder. Since solar energy levels fluctuate with the seasons, solar thermal is usually paired with a boiler or immersion heater to top up your hot water during colder months.
⚠️ Important note: Solar thermal systems are typically designed to provide hot water for taps, baths, and showers – not to heat your radiators. While it’s technically possible in specialist systems (like underfloor heating or those with large thermal stores), this is rare in standard UK homes.
How Does It Work?
The process is surprisingly straightforward. Solar collectors on your roof absorb heat from the sun. Inside these panels flows a heat-transfer liquid (usually a mix of water and antifreeze) that’s warmed by the sun. This fluid is pumped into a coil inside your hot water cylinder, where it transfers its heat to the water. The cooled fluid then returns to the panels to be heated again.
There are two main types of solar collectors: flat plate panels, which are more affordable and widely used, and evacuated tubes, which are more efficient, especially in colder weather, but typically cost more.
What Are the Benefits?
Installing a solar thermal system can reduce your reliance on fossil fuels, lower your carbon emissions, and shave money off your energy bills. On average, a well-designed system can provide up to 90% of your hot water needs in summer, although this drops to around 25% in winter. Across the year, you could expect about 50% of your hot water to be solar-heated.
For households that use electric immersion heaters or oil boilers for water heating, the savings can be significant and you’ll be reducing your carbon footprint by up to 550kg of CO₂ each year.
Solar thermal is also a long-lasting and relatively low-maintenance technology. Systems typically last 20 to 25 years, and they’ve been widely used across Europe for decades.
Is Solar Thermal Right for Your Home?
Not every home will be suitable, so it’s important to assess a few practicalities before making a decision.
- The first consideration is roof orientation. Solar thermal collectors work best on south-facing roofs, but east or west-facing positions can still offer good performance. You’ll need about five square metres of unobstructed space with good sun exposure.
- Next, think about your hot water usage. The technology makes most sense in homes with higher water demand – typically households of three or more people. If you live alone and take quick showers, the payback period may be too long to justify the cost.
- You’ll also need space for a hot water cylinder. If you already have one (such as with a conventional boiler), it might need upgrading to a twin-coil version. If you currently have a combi boiler, the situation is more complicated: most combi systems aren’t compatible with solar thermal unless you also install a separate hot water tank.
- Finally, in terms of planning rules, most homes in Lancashire can install solar thermal under permitted development rights. However, if your property is listed or in a conservation area, you’ll need to check with your local planning office.
What Does It Cost and Will You Save?
A typical domestic solar thermal installation costs between £4,000 and £6,000, depending on the system size and property layout. While upfront costs can feel steep, the system begins saving you money from day one.
For a family using a gas boiler, annual savings might be around £75 to £100. If you’re using oil or electric heating, you could save up to £180 per year. Over the lifespan of the system, you’re looking at carbon savings of more than six tonnes!
At current energy prices, the payback period for a standard system ranges from 20 to 40 years, depending on how efficiently the system is used and how high your hot water demand is. It won’t suit every household financially, but for those planning long-term or prioritising sustainability, it can be a solid investment.
Are There Any Grants or Support Available?
Unfortunately, solar thermal no longer benefits from major government incentives.
The Renewable Heat Incentive (RHI), which supported installations with ongoing payments, closed to new applications in 2022. Its replacement, the Boiler Upgrade Scheme, only covers heat pumps and biomass boilers.
However, there is one perk worth knowing: until March 2027, solar thermal installations are VAT-free, making it slightly more affordable than it used to be.
Maintenance: What to Expect
Once installed, solar thermal systems are generally easy to look after. Most manufacturers recommend a check every five years, which includes flushing the system and replacing the antifreeze fluid. Some homeowners opt for an annual service for peace of mind, especially in hard water areas.
The system should run quietly in the background. Your installer will show you how to monitor the control panel and what to look out for, such as low pressure or warning lights. It’s also a good idea to use the system’s ‘holiday mode’ if you’re away for an extended period.
How to Get Started
If you’re considering solar thermal, it’s a good idea to speak to a few certified installers to see what’s possible for your home. Always look for MCS-certified professionals (Microgeneration Certification Scheme) and try to get at least three quotes to compare design and cost.
At Greener Homes in Lancashire, we offer free, impartial advice to help you understand whether solar thermal is right for your household and explore other options like solar PV, heat pumps, or improved insulation..
Give us a call, and we’ll help point you in the right direction – whether that’s answering your questions, recommending next steps, or helping you find trusted local installers.
You don’t have to make these decisions alone.
Solar thermal won’t be the right fit for everyone. But for homes with good roof space, high water demand, and a compatible boiler system, it can provide a long-term, low-carbon way to heat your water.