Heat pump vs biomass boiler

A heat pump and a biomass boiler are the two technologies the Boiler Upgrade Scheme funds for a home that is off the gas grid, and they are the two most different ways of heating a house that the same grant can buy. One runs on electricity and moves heat from the air or the ground. The other burns wood and makes heat on site. Both must provide space heating and hot water, and both must be capable of meeting the full demand of the property¹.

The grant position is the first thing households compare. The scheme pays £7,500 off the cost and installation of an air source heat pump and £5,000 off a biomass boiler¹. For eligible off-gas grid properties replacing oil or liquefied petroleum gas, an air source or ground source heat pump can attract an uplifted grant of £9,000, a figure that does not extend to biomass². One grant is available per property, and the scheme runs in England and Wales only¹.

The efficiency gap is the second. Government guidance states heat pumps are typically more than three times as efficient as a gas boiler, and the Climate Change Committee puts the figure at around three to four times³. The same guidance notes the energy needed can be less than a third of that required by a gas boiler to produce an equivalent amount of heat⁵. A biomass boiler has no equivalent multiplier: it converts wood into heat at a rate set by the appliance and the fuel.

What each technology offers a UK household

The Boiler Upgrade Scheme offers upfront capital grants to property owners to install heat pumps and, in limited circumstances, biomass boilers, replacing fossil fuel heating with a focus on off-gas grid homes⁸. Biomass is the narrower route by design. Ofgem guidance states biomass boilers may only be installed in properties in rural areas, and the emissions certificate must show particulate matter no higher than 30g/GJ net heat input and NOx no higher than 150 g/GJ net heat input². A heat pump carries no such location restriction.

Both technologies must distribute heat using a liquid, and both must provide space and hot water heating to the property⁹. That rules out warm air systems and any biomass stove that heats one room. The eligible technologies under the scheme are air-to-water heat pumps, air-to-air heat pumps, ground source heat pumps including water source heat pumps and shared ground loops, and biomass boilers². Air-to-air heat pumps are eligible for residential properties only, and self-build properties are eligible for heat pumps only².

Take-up tells its own story. Since the scheme launched, air source heat pumps account for 67.4% of accreditations, ground source 13.2%, biomass 11.1% and solar thermal 8.3%¹⁰. The same split appears in the 2023-24 figures¹¹. Public attitudes data suggests part of the reason: 36% of owner-occupiers say they do not know enough about biomass boilers to decide, against 38% for hybrid heat pumps¹².

Specifications: what the scheme requires

The specification rules are where the two technologies diverge most sharply, and they are set by the scheme rather than by the manufacturer.

The capacity ceilings matter for larger properties. An individual heat pump system is capped at 45 kWth, a multi heat pump system at 70 kWth, and a shared ground loop system at 300 kWth total with each connected heat pump not exceeding 45 kWth². An individual biomass boiler system is capped at 45 kWth². Above those figures the scheme does not apply.

The heat pump efficiency test is measured in situ: air-to-water and ground source heat pumps must achieve a seasonal coefficient of performance of at least 2.8². There is no equivalent performance threshold for biomass, which is regulated instead on what comes out of the flue. For the metering arrangements that applied under the earlier Renewable Heat Incentive, heat output from a biomass boiler and any additional heaters on the same distribution system was measured to Class 3 of the Measuring Instruments Directive, with heat metering resolution no finer than 1Wh accuracy class¹³.

What the warranty and scheme conditions cover

Neither technology carries a scheme-backed warranty. What the Boiler Upgrade Scheme imposes is a set of conditions on the installation, and the manufacturer's own warranty sits separately on top of that.

The application is a two-stage process: the installer submits a voucher application, Ofgem issues a voucher, the installer submits a voucher redemption application, and the installer receives the grant payment¹⁴. Installation must follow within 3 months for air-to-water heat pumps, air-to-air heat pumps and biomass boilers⁷. The application must then be properly made within 120 days of the commissioning date².

Several conditions void eligibility outright. Properties classed as social housing are not eligible, including shared ownership properties⁷. A property will not be eligible if a previous BUS grant has already been received for installing a heat pump or biomass boiler at the same address, and only one voucher can be redeemed per property². The previous heating system being replaced must have been a fossil fuel-based system or an electric heating system that does not include a heat pump². Hybrid systems are excluded: government guidance states you cannot get a grant for a hybrid heat pump system, for example a combination of gas boiler and air source heat pump, and integrated fossil fuel hybrid systems do not meet the definition of an air source or ground source heat pump¹⁵.

The installer must be certified by the Microgeneration Certification Scheme¹. All heating systems installed under the scheme must meet the relevant MCS standards approved and published by the Secretary of State². From 28 April 2026, properties are no longer required to have a valid energy performance certificate to apply, and BUS heat pumps can be installed alongside supplementary heating appliances provided those appliances are not fossil fuel based².

What each route costs

The published cost figures are uneven, and that unevenness is itself the finding. A parliamentary committee report gives around £11,600 for an average heat pump, describing it as four times more expensive than a gas boiler⁶. The same comparison appears in the committee's summary¹⁷. That is a 2024 figure and covers installation, not running cost.

For biomass boilers there is no equivalent published UK figure. Prices are installer-quoted, and the grant of £5,000 is applied against whatever the installer quotes¹. The absence of a benchmark is worth stating plainly rather than filling with an estimate.

The grant structure is where the comparison becomes concrete:

• Air source heat pump: £7,500 off the cost and installation¹
• Biomass boiler: £5,000 off the cost and installation¹
• Air-to-air heat pump: £2,500¹⁸
• Uplifted grant for eligible off-gas grid properties: £9,000 for air source or ground source heat pumps²
• Standard grant for eligible properties that do not qualify for the uplift: £7,500²

The uplifted amount applies where the previous heating system being replaced was fuelled by oil or liquefied petroleum gas². It is available for applications properly made on or after 21 July 2026². Biomass does not attract the uplift, so an off-gas grid household replacing oil faces a £4,000 difference in grant between the two routes before any installation cost is considered.

The scheme opened on 23 May 2022 and closes on 30 December 2029¹. Ofgem is the scheme administrator, and applications are made to Ofgem for a grant voucher¹. General queries go to the BUS Enquiries team⁷.

Where the two routes stand on company and scheme status

There is no single manufacturer to assess here, because both categories span many makers. What can be assessed is the status of the scheme and the pattern of accreditations.

The Boiler Upgrade Scheme is active and administered by Ofgem, providing upfront capital grants towards the cost of installing approved heat pumps¹⁹. It launched on 23 May 2022 to support the decarbonisation of heat in buildings¹⁹. The most recent quarterly report covers the period from 1 May 2026 to 31 July 2026²⁰. The scheme provides upfront capital grants to support the installation of heat pumps and biomass boilers in homes and non-domestic buildings²⁰.

The accreditation split is the clearest signal of where the market sits. Biomass accounts for 11.1% of accreditations since scheme launch, against 67.4% for air source heat pumps and 13.2% for ground source¹⁰. That is a minority route, and the rural-only restriction plus the absence of an uplifted grant explains much of it.

On the wider policy picture, the government is providing grants to encourage property owners to install low carbon heating systems such as heat pumps¹⁵. The scheme is open to domestic and small non-domestic properties¹⁵. The majority of government-supported heat pump installations in the year ending June 2025 came through the Energy Company Obligation, at 31% of installations²².

What each route means for household energy independence

This is where the two technologies part company most completely, and the difference is about what a household still depends on after installation.

A heat pump replaces a fuel delivery with an electricity supply. It does not remove dependence on the grid, and it does not remove dependence on a supplier. What it changes is the fuel: no oil tank, no LPG bottle, no wood store, no flue. Government guidance states heat pump technology currently offers a carbon saving of up to 65% compared with a gas boiler²³, and separately that heat pumps offer up to 70% less CO2 over 15 years than a gas boiler with zero emissions at point of use²⁴. The Scottish Government's Heat in Buildings Strategy states the higher efficiency of a heat pump means the amount of energy needed can be less than a third of that needed by a gas boiler to produce an equivalent amount of heat⁵.

A biomass boiler replaces a fossil fuel delivery with a wood delivery. It removes dependence on gas, oil and LPG, and it removes dependence on the electricity grid for the heat itself, though the boiler still needs power for pumps, fans and controls. What it introduces is a new supply chain: pellet or log suppliers, a fuel store, and a flue. For a household with access to a reliable local wood supply, that is a genuine form of independence. For one without, it is a different dependency rather than a removed one.

The carbon accounting differs too. A heat pump's emissions fall as the grid decarbonises, because the fuel is electricity. A biomass boiler's emissions are set at the point of combustion and do not improve with grid changes. The Climate Change Committee's seventh carbon budget places heat pumps at around three to four times more efficient than gas boilers, which is the basis for lower household energy bills as well as lower emissions⁴.

The honest summary for a household weighing the two: a heat pump trades a fuel dependency for an electricity dependency and a supplier relationship, with a grant of £7,500 or £9,000 and a published average cost of around £11,600¹. A biomass boiler trades a fossil fuel dependency for a wood supply dependency, with a grant of £5,000, a rural-only restriction, and no published UK cost benchmark¹. Neither removes dependence entirely. Both are eligible under the same scheme, and the scheme's own rules make the choice narrower than it first appears.