Solar thermal hot water costs roughly £3,000 to £6,000 installed and covers only part of a home's hot water. Biomass boilers suit mainly rural off-gas homes, and the Boiler Upgrade Scheme biomass grant is £5,000. For most homes, a heat pump or solar PV is now the simpler choice.
Both technologies need space, a hot water cylinder or fuel store, and an MCS or HETAS-registered installer.
Solar thermal hot water
How it works
Solar thermal panels heat a fluid that passes through a coil in a hot water cylinder. They provide hot water, not electricity, and typically cover around 60% of a home's yearly hot water needs, with most of that in spring and summer. A boiler or immersion heater tops up the rest.
What it costs
Installed costs are generally reported at about £3,000 to £5,000 for flat-plate collectors and £4,000 to £6,000 for evacuated tube systems, with some sources reporting up to £8,000. If your cylinder needs replacing with a twin-coil model, add roughly £800 to £1,500. Annual hot water savings are typically reported at roughly £300 to £530, depending on the fuel you replace, which implies a long payback.
Who it suits
- Homes with a hot water cylinder and a south, east or west facing roof.
- Homes using expensive fuels such as electricity, oil or LPG for hot water.
It is not suited to combi boiler homes without a cylinder. Many installers now recommend solar PV with a hot water diverter instead, which covers hot water in summer and gives electricity all year. The number of MCS-certified solar thermal installations has fallen sharply in recent years, so check that local installers still offer it.
See our solar thermal installer page.
Biomass boilers
How they work
A biomass boiler burns wood pellets, logs or chips to heat your home and hot water. Pellet boilers can be automatically fed from a hopper or store. Log boilers need loading by hand and often work with a buffer tank.
Cost and grant
Biomass boilers usually cost as much as or more than a heat pump once fuel storage and flue work are included, so get several quotes. The Boiler Upgrade Scheme offers £5,000 towards a biomass boiler, but only for eligible rural, off-gas-grid homes replacing fossil fuel heating. Ofgem guidance confirms that biomass boilers must be standalone systems in rural, off-gas-grid properties, that self-build properties cannot receive funding for them, and that the £9,000 off-gas uplift applies to heat pumps only. For this purpose Ofgem treats a property as rural if it is outside a settlement of more than 10,000 people, checked against the ONS rural-urban classification for its address. Rules and values change, so confirm on the Boiler Upgrade Scheme page and gov.uk.
Practical points
- Fuel storage and delivery: you need dry storage and vehicle access for deliveries.
- Running and maintenance: regular ash removal, cleaning and an annual service are required.
- Fuel price and quality: pellet and log prices vary, and good-quality fuel matters.
- Smoke control areas: in a smoke control area, wood is an unauthorised fuel that can only be burned in a Defra-exempt appliance, and only the fuels the manufacturer says it can use. Gov.uk says you may have to pay a penalty of up to £300 if your chimney releases smoke, and you can be fined up to £1,000 for buying unauthorised fuel for a non-exempt appliance. Ask your local council whether you are in one and check the exact model is on the Defra exempt list before you buy.
- Air quality: consider emissions and neighbours, particularly in towns.
- Building Regulations and flues: solid fuel appliances fall under Part J, and installers are normally HETAS-registered. See the UK Building Regs guide.
How they compare
| Solar thermal | Biomass boiler | Heat pump | |
|---|---|---|---|
| Provides | Hot water only | Heating and hot water | Heating and hot water |
| Indicative cost | £3,000 to £6,000 | Quote-dependent; often similar to a heat pump or more | £7,000 to £14,000 (ASHP) |
| Grant | None in the main schemes | £5,000 BUS for eligible rural homes | £7,500 BUS (£9,000 for eligible off-gas homes to 31 March 2027) |
| Best for | Homes with a cylinder and expensive hot water fuel | Rural homes with storage space | Most well-insulated homes |
See the heat pump guide before committing to either option.
Sources and further reading
- Ofgem: Boiler Upgrade Scheme installer guidance (V5.1) Grant values, eligibility, biomass rules and the voucher end date
- GOV.UK: Apply for the Boiler Upgrade Scheme Who can apply and what the grant covers
- The Boiler Upgrade Scheme (England and Wales) (Amendment) Regulations 2026 The April 2026 changes, including the removal of the EPC requirement
- GOV.UK: smoke control area rules Burning wood in smoke control areas and penalties
External links open in a new tab. Last checked October 2026.
Frequently asked questions
How much does solar thermal cost in the UK?
Typically about 3,000 to 6,000 pounds installed in 2026, with some sources reporting up to 8,000, and extra if the hot water cylinder needs replacing.
Is solar thermal still worth it?
Rarely on cost alone. It covers only part of your hot water, and solar PV with a hot water diverter is often recommended instead. Compare quotes.
What is the Boiler Upgrade Scheme grant for a biomass boiler?
5,000 pounds for eligible rural, off-gas-grid homes replacing fossil fuel heating. It does not apply to self-build properties. Check gov.uk for current terms.
Can I install a biomass boiler in a smoke control area?
Only a Defra-exempt appliance, burning the fuel its manufacturer specifies, may burn wood or other unauthorised fuel in a smoke control area. Check with your local council and the Defra exempt appliance list before you buy.
Do I need a hot water cylinder for solar thermal?
Yes. Combi boiler homes without a cylinder are not suitable unless a cylinder is added.