Solar PV vs Solar Thermal: What's the Difference? (UK Guide)
Both use sunlight — but they do completely different things. Solar PV (photovoltaic) panels generate electricity for your home and export surplus to the grid. Solar thermal collectors heat your domestic hot water. Understanding the difference is the first step to choosing the right system, or deciding if you want both.
At a glance
| Solar PV | Solar thermal | |
|---|---|---|
| What it does | Generates electricity | Heats domestic hot water |
| Typical installed cost | £6,000–£10,000 (4kWp) | £3,000–£5,000 (2-panel system) |
| Annual saving | £400–£800 on electricity | £80–£200 on hot water heating |
| Payback period | 7–11 years | 15–25+ years |
| Can power appliances | Yes | No |
| Can power heating system | Via heat pump or storage heater | Contributes to hot water only |
| Grant available | 0% VAT; ECO4 for eligible households | 0% VAT; some ECO4 paths |
| MCS certification required | Yes (for SEG payments and grants) | Yes (for grants and quality) |
Verdict:For most UK homes in 2026, solar PV is the better investment — shorter payback, greater versatility, and the ability to pair with battery storage and EV charging. Solar thermal is still a valid option for households with high hot water demand or as a complement to existing solar PV — but standalone solar thermal has been largely superseded by solar PV + diverter combinations.
How solar PV works
Solar PV panels contain semiconductor cells that convert sunlight directly into DC electricity. An inverter converts this to AC electricity usable by your home's appliances. Any surplus is exported to the grid via your Smart Export Guarantee tariff. A battery storage system can store surplus generation for evening use. Modern panels generate electricity from diffuse daylight as well as direct sun — they work year-round in the UK, generating most output in spring and summer.
How solar thermal works
Solar thermal collectors use sunlight to heat a fluid (typically a glycol-water mixture) that circulates through a coil in your hot water cylinder, transferring heat to the stored water. Most UK systems are flat-plate collectors (simpler, cheaper, fine for the UK climate) or evacuated tube collectors(more efficient in cold or cloudy conditions, higher cost). A solar thermal system typically provides 40–70% of a household's annual hot water demand — the remainder is topped up by your boiler or immersion heater.
Which should you choose?
For most homes in 2026, solar PV is the better choice. The cost has fallen dramatically over the past decade, payback periods are shorter, and electricity is much more versatile than hot water — it can run any appliance, power an EV, or feed a heat pump.
Solar thermal makes more sense when:
- You already have solar PV and want to add a complementary hot water system
- Your primary concern is reducing gas use specifically for hot water
- You have a south-facing roof with limited space and high hot water consumption
If you are considering replacing your boiler with a heat pump, solar thermal is generally not the right pairing — a heat pump already provides hot water efficiently, and an immersion heater can use excess PV generation to top up the cylinder for free.
Common questions
Can I have both solar PV and solar thermal?
Yes, and some homes do — particularly larger households with high hot water demand. However, most installers now recommend solar PV with a battery or a diverter (e.g. Immersun, Eddi) that uses surplus PV generation to heat the hot water cylinder, achieving similar hot water benefits without the additional complexity and cost of a separate thermal system.
Is there a grant for solar thermal in the UK?
There is no dedicated solar thermal grant for most households in 2026 (the Renewable Heat Incentive closed in 2022). Solar thermal does qualify for 0% VAT. Eligible low-income households may be able to access solar thermal as part of an ECO4 package. The Boiler Upgrade Scheme does not cover solar thermal.
How long does a solar thermal system last?
A well-maintained solar thermal system typically lasts 20–25 years. The collector panels are very durable; the pump and expansion vessel components may need replacing over the system's lifetime. The storage cylinder usually lasts 15–20 years.
Does solar thermal need planning permission?
Usually no — solar thermal panels are permitted development on most properties. Exceptions include listed buildings, some conservation areas, and properties where the installation would exceed certain size limits. Your installer will confirm what applies to your property.
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