Solar panels and solar panels. There are two quite different technologies that both go on your roof, both point at the sky, and both use sunlight as their fuel — and most people have only really heard of one of them. Solar PV (photovoltaic) converts sunlight into electricity. Solar thermal converts sunlight directly into heat. They’re used for different purposes, installed by different people, and right now in 2026 they’re in rather different positions in the UK market.
Solar thermal never had its big cultural moment the way solar PV did. It didn’t benefit from the same feed-in tariff excitement, and the rapid cost decline of solar PV panels in recent years has made some people write it off entirely. That’s a mistake. For specific circumstances — a household with high hot water demand that’s considering a heat pump, or a home that wants to reduce gas use without the full heat pump commitment — solar thermal is worth a serious look.
What Solar Thermal Actually Does
A solar thermal system uses roof-mounted collectors to capture heat from sunlight and transfer it to your hot water cylinder. The collectors circulate a heat transfer fluid (typically a glycol antifreeze mixture) that absorbs solar energy and passes it through a coil inside your hot water tank. Your hot water gets heated, the fluid cools down, and the cycle continues.
What it does not do is generate electricity. If your gas boiler breaks down, solar thermal cannot run your lights or charge your phone. It heats water. That single, specific function is both its strength and its limitation.
There are two main collector types:
Flat plate collectors are the simpler and cheaper option: a flat, insulated panel with a dark absorber plate under a glass cover, typically fitted flush to the roof. These are adequate for most UK climates and are the most commonly installed type.
Evacuated tube collectors use glass vacuum tubes to reduce heat loss from the absorber. They perform better in cold and overcast conditions because the vacuum minimises conductive heat loss, and they can reach higher temperatures. They’re also more expensive. For the UK’s grey winters, evacuated tubes tend to perform meaningfully better than flat plates on the days when you need them most.
A typical UK installation uses 2-4 square metres of collector area for a two- to four-person household.
What UK Homes Can Realistically Expect
The UK is not Spain. Our solar resource varies considerably by region and season, and solar thermal only generates heat when there’s sun. A well-sized, south-facing solar thermal system in the UK will typically cover 50-70% of a household’s annual hot water energy demand. The proportion is higher in summer (often over 90% on good days) and lower in winter, when you’ll still need a backup heat source — your boiler, heat pump, or immersion heater.
That means solar thermal isn’t a standalone solution. It works alongside your existing heating system, reducing the load on it rather than replacing it. On a hot July day, you may not touch your boiler at all for hot water. In December, you’ll rely on it more heavily, with the solar thermal contributing when the sun comes out.
Costs in 2026
A solar thermal system in the UK typically costs between £3,000 and £6,000 fully installed, depending on system size and collector type. Evacuated tube systems sit toward the top of that range; flat plate toward the bottom.
There is no government grant specifically for solar thermal in 2026. The Boiler Upgrade Scheme covers heat pumps and biomass boilers, not solar thermal. Some local authority schemes and energy efficiency loan products (including the government’s Warm Homes Plan for lower-income households) may cover solar thermal in specific circumstances, but you’d need to check eligibility with your installer and local council.
Running costs are minimal — a small circulation pump uses very little electricity, and the glycol antifreeze needs replacing roughly every five years at modest cost. Expected system lifespan is 20-25 years.
When Solar Thermal Makes Sense
You have high hot water demand. Larger households, homes with baths rather than showers only, or properties running a small guest accommodation see better returns because the solar energy offsets more actual gas or electricity use.
You’re also installing a heat pump. This is where solar thermal becomes particularly interesting. Heat pumps are efficient at heating space, but they’re less efficient at producing the high temperatures needed for hot water (above 55°C). Pairing a heat pump with solar thermal lets the solar collectors cover the majority of hot water demand in summer, keeping the heat pump focused on space heating and avoiding the inefficiency hit from constant high-temperature hot water runs.
You want to reduce gas use incrementally. If replacing your boiler with a heat pump isn’t financially viable right now, solar thermal reduces your gas consumption for hot water immediately and at lower upfront cost than a heat pump installation.
When it makes less sense: if your hot water demand is low, you live in heavy shade, or your south-facing roof space is already taken by solar PV panels that are generating electricity income, the maths may not work in solar thermal’s favour.
Finding an Installer
Solar thermal installers should be registered with the Microgeneration Certification Scheme (MCS). An MCS-certified installation is required for any grant application and guarantees that the installer meets quality and competency standards. The MCS website maintains an installer finder — search for solar thermal specifically, as not all solar installers cover both PV and thermal.
It’s worth getting at least two or three quotes. Installation complexity varies considerably depending on your existing hot water cylinder setup; some homes need a replacement cylinder with the right coil configuration, which adds cost.