Solar thermal vs solar PV: which is right for your UK home?

Solar thermal and solar PV both sit on your roof and both use the sun, but they do completely different jobs. Solar thermal heats water: it warms a fluid that heats your hot-water cylinder. Solar PV generates electricity you can use anywhere in the house, store in a battery, or sell back to the grid. For most UK homes in 2026, solar PV is the more flexible choice, and if hot water is your priority you can add a cheap "diverter" that sends surplus PV electricity to your immersion heater, getting solar hot water as a by-product of a system that also powers the house. Solar thermal still has its place, but it's now a narrow one.

This page is the straight comparison: what each technology does, what they cost, how much roof they need, what they save, the grants reality (which favours neither cleanly), and the honest verdict. It's the companion to our fuller solar thermal guide, which goes deeper on how solar water heating works.

A note on our tools: our roof check and Solarable Report are built around solar PV. They'll tell you whether your roof suits panels and roughly what they'd generate. They don't assess thermal systems, so take the thermal principles here as general guidance and get an MCS-certified installer to survey before you commit either way.

The core difference: heat vs electricity

Everything else follows from this one distinction.

• Solar thermal makes heat, and only heat, for your hot water. A roof collector warms a fluid, that fluid heats a coil in your hot-water cylinder, and the result is a tank warmed by the sun instead of (or as well as) your boiler. It does one thing.
• Solar PV makes electricity. That electricity runs anything electrical in your home, and any surplus can charge a battery, power an EV, heat your water through a diverter, or be exported for cash. It does many things.

That's the whole story in miniature: thermal is a specialist, PV is a generalist.

Side by side

	Solar thermal	Solar PV
What it makes	Heat for hot water only	Electricity for the whole home
Typical cost	£3,000–£6,000 (up to ~£8,000)	£5,000–£10,000 for a typical system
Roof space	~3–5 m² collector	~20 m² for a 4 kWp array
What it offsets	Part of your hot-water bill	Any daytime electricity use
Coverage	~50–60% of annual hot water	Broadly an average home's annual electricity use (on paper)
Grant	None (BUS excludes it)	None directly, but earns SEG export income
Export income	No (heat can't be exported)	Yes, via the Smart Export Guarantee
VAT	0% until 31 March 2027	0% until 31 March 2027
Needs a hot-water cylinder	Yes, essential	No (but useful for a diverter)

The numbers above are typical UK ranges to plan around, not a quote for your home. Only an installer survey turns them into a real figure.

Cost and roof space

Solar thermal is cheaper up front, typically £3,000–£6,000 installed (occasionally up to around £8,000 with an evacuated-tube collector and a new cylinder), and it uses less roof: 3–5 square metres of collector. If your roof is small or you want to dedicate only a corner of it to solar, that compactness is a genuine point in its favour.

Solar PV costs more, typically £5,000–£10,000 for a domestic system depending on size and whether you add a battery, and it wants more roof, around 20 square metres for a common 4 kWp array. But it's doing far more for the money. This is the recurring theme: thermal is cheaper and smaller because it does less.

What each actually saves

Here's where the comparison gets decisive, and where a lot of pages are vague.

Solar thermal only ever offsets the cost of heating water, which is a modest slice of most homes' energy use. A well-sized system supplies around 50–60% of a household's annual hot water, but that average hides a lopsided year: it can cover nearly all your hot water on long summer days and very little in deep winter. If you heat water with cheap mains gas, the annual saving is small (often in the low £100s) and payback can stretch to decades. If you're on more expensive electricity, oil, or LPG, the case improves, but payback still commonly lands in the 15–25 year range. We lay this out fully in the solar thermal guide.

Solar PV offsets electricity, which is both used more and priced higher per unit than gas, and it earns money on the surplus through the Smart Export Guarantee. A typical system generates roughly what an average home uses over a year, cuts your daytime grid draw, and typically pays back faster than thermal. For the detail on output, see how much electricity a solar panel produces.

The grants reality: it favours neither, cleanly

A common myth is that one of these attracts a grant. In 2026, the honest position:

• The Renewable Heat Incentive (RHI) is gone. The scheme that used to pay solar thermal owners for the heat they generated closed to new applications on 31 March 2022. You cannot get it on a new install.
• The Boiler Upgrade Scheme (BUS) does not cover solar thermal. BUS is worth £7,500 towards a heat pump, but it funds heat pumps and biomass, not standalone solar water heating.
• Neither PV nor thermal gets a direct install grant. What PV does have is an ongoing income stream (SEG export payments); thermal has no equivalent, because heat can't be exported.
• Both get 0% VAT as energy-saving materials, currently until 31 March 2027, after which it's expected to revert to 5% unless extended.

So grants don't tip the choice. But the income side does: PV earns from its surplus, thermal earns nothing ongoing. Over 20 years that gap compounds in PV's favour.

The move most people should make: PV plus a diverter

If your real goal is cheaper, greener hot water, the modern answer usually isn't solar thermal. It's solar PV with a hot-water diverter.

A diverter (an iBoost, Eddi, or similar, typically a few hundred pounds) senses surplus solar electricity you'd otherwise export and sends it to your existing immersion heater, heating your hot-water tank for free with power you've already generated. One roof technology then does two jobs: it powers your home and heats your water. You keep all of PV's advantages (whole-home electricity, export income, battery and EV options, wider roof suitability) and get solar hot water as a bonus, often with similar or better coverage than a standalone thermal system.

The one requirement is a hot-water cylinder with an immersion heater. If you have a combi boiler and no cylinder, a diverter has nothing to heat, which is the same limitation that makes solar thermal awkward for combi homes. In that case PV still stands on its own for electricity; the hot-water angle just doesn't apply.

The honest verdict

For the mainstream UK home in 2026, solar PV, optionally with a hot-water diverter, is the more flexible and usually the smarter buy. It does more, earns money on its surplus, suits a wider range of roofs, and typically pays back faster. Solar thermal is a sound, durable technology, but it's a specialist tool for a narrower job.

Solar thermal can still make sense in specific cases: a home that already has a suitable twin-coil cylinder, a small roof where you'd rather dedicate a compact area purely to hot water, or an off-gas home paying a lot to heat water with electricity or oil. Outside those, the money usually works harder as PV.

If you're weighing it up, the fastest useful step is to see what your roof could do for electricity. Our roof check gives a direction and suitability read for solar PV in about a minute, the savings calculator puts a realistic range on it, and our installer directory lists MCS-certified installers covering your postcode. If hot water really is the whole question, ask an installer to quote solar thermal against a PV-plus-diverter alternative so you're comparing real numbers, not brochures.

Frequently asked questions

What's the difference between solar thermal and solar PV?

Solar thermal heats water: a roof collector warms a fluid that heats your hot-water cylinder, so it only offsets your hot-water bill. Solar PV generates electricity you can use anywhere in the home, store in a battery, use to charge an EV, send to your immersion heater via a diverter, or export for cash. Thermal does one job; PV does many.

Is solar thermal or solar PV better for a UK home?

For most UK homes in 2026, solar PV is the better choice because it's far more flexible, earns export income on its surplus, and typically pays back faster. If your main aim is hot water, PV plus a cheap hot-water diverter usually beats standalone solar thermal, giving you solar hot water as a by-product of a system that also powers the house. Solar thermal still suits specific cases, such as a home with an existing compatible cylinder or an off-gas home on expensive fuel.

Can I have both solar thermal and solar PV?

Technically yes, but you rarely need both, and they compete for the same roof space. If hot water is the goal, most people are better off putting the whole roof to PV and adding a hot-water diverter, which heats your tank with surplus electricity for a few hundred pounds. That gets you both electricity and solar hot water from one system, rather than splitting the roof between two.

Are there grants for solar thermal or solar PV in 2026?

Neither gets a direct install grant. The Renewable Heat Incentive that once paid solar thermal owners closed to new applicants on 31 March 2022, and the Boiler Upgrade Scheme funds heat pumps, not solar thermal. Both technologies get 0% VAT until 31 March 2027. The difference is income: solar PV earns money on exported surplus through the Smart Export Guarantee, while solar thermal has no ongoing payment because heat can't be exported.

What is a hot-water diverter and why does it matter here?

A hot-water diverter (such as an iBoost or Eddi) senses surplus solar PV electricity you'd otherwise export and sends it to your immersion heater, warming your hot-water tank for free. It typically costs a few hundred pounds and needs a cylinder with an immersion heater. It's the reason solar PV can do solar thermal's job as a bonus, and a big part of why PV has overtaken thermal for most homes.

Related

• Solar thermal panels UK: how solar water heating really stacks up
• How much electricity does a solar panel produce?
• Smart Export Guarantee: how UK solar exports actually pay
• A homeowner's guide to going solar in the UK (2026)
• Is my roof suitable for solar?
• Estimate your savings