Boiler Upgrade Scheme or ECO4 for a heat pump?

A heat pump can be funded through the Boiler Upgrade Scheme or through ECO4, but not through both for the same installation. Ofgem guidance states that funding from the two schemes cannot be blended for the same measure or included within an ECO4 project¹. The choice is therefore a real one, and it turns on where the property is, who lives in it, what heating it replaces and whether the household qualifies for supplier-funded work at all.

The Boiler Upgrade Scheme is the simpler of the two. It pays a fixed upfront capital grant towards an approved heat pump, is administered by Ofgem, and covers England and Wales only². The standard grant is £7,500 for air-to-water and ground source heat pumps, and £2,500 for air-to-air systems³. From 21 July 2026, eligible off-gas grid properties replacing oil or LPG heating can apply for an uplifted grant of £9,000, in place until 31 March 2027².

ECO4 works differently. It is not a grant scheme in the ordinary sense: it is the energy supplier that decides which retrofit projects to fund, and the funding is limited⁴. It runs until 31 December 2026 following a nine-month extension, and some councils already state that the grant is closed in their area⁵. ECO4 delivers to homes in Great Britain, so it covers England, Scotland and Wales but not Northern Ireland⁷.

What each scheme offers a UK household

The Boiler Upgrade Scheme exists to make low carbon heating more affordable by offering upfront grants, and it supports heat pumps and, in limited circumstances, biomass boilers⁹. It launched on 23 May 2022 and provides upfront capital grants towards the cost of installing approved heat pumps¹⁰. Applications go to Ofgem as scheme administrator, and the scheme has been extended to 2030². The published closing date for applications is 30 December 2029 at 11:59pm¹¹.

ECO4 is the fourth Energy Company Obligation and is administered by Ofgem¹². It funds energy efficiency measures such as heating improvements and insulation, and its measures include insulation, boilers and central heating, and solar and renewable technologies⁴. It was launched in 2022 and delivers energy efficiency and heating measures to homes in Great Britain⁷. The scheme is worth £4 billion⁸.

The two schemes answer different questions. The Boiler Upgrade Scheme asks whether a property has a suitable heat pump installation and a previous heating system worth replacing. ECO4 asks whether a household qualifies under one of its eligibility routes and whether a supplier chooses to fund the work. That difference explains why a household can be eligible for one and not the other, and why the two are kept apart in the rules.

Specifications: what each scheme requires

The Boiler Upgrade Scheme sets technical conditions that are published and checkable in advance. Eligible technologies 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-water and ground source heat pumps must achieve an in situ seasonal coefficient of performance of at least 2.8². Capacity limits are 45 kWth for an individual heat pump system, 70 kWth for a multi heat pump system, and 300 kWth total for shared ground loop systems, with each connected heat pump not exceeding 45 kWth². Biomass boilers are capped at 45 kWth, may only be installed in rural areas, and must meet emissions limits of 30g/GJ net heat input for particulate matter and 150 g/GJ for NOx².

All heating systems installed under the scheme must meet the relevant MCS standards approved and published by the Secretary of State². 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. From 28 April 2026, BUS heat pumps can be installed alongside supplementary heating appliances, provided those appliances are not fossil fuel based². Hybrid heat pump systems, such as a gas boiler combined with an air source heat pump, cannot receive a grant¹⁵.

ECO4's specifications are set out in delivery guidance rather than in a single eligibility page. The current delivery guidance is version 4.0, dated 26 March 2026¹⁶. One technical distinction matters for heat pumps: an air-to-air system is not considered to be a renewable system in ECO4¹⁰. That places air-to-air heat pumps outside the renewable measures ECO4 recognises, even though the Boiler Upgrade Scheme pays £2,500 towards them.

Eligibility: who qualifies for which

Boiler Upgrade Scheme eligibility is property-based. New build properties which the developer is still building are not eligible, though a household moving into a finished new build with a fossil fuel boiler may be able to get a grant for a heat pump¹⁷. Properties classed as social housing are not eligible, and this includes shared ownership properties⁶. 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. Self-build properties are only eligible for heat pumps, not biomass². From 28 April 2026, properties are no longer required to have a valid EPC to apply².

ECO4 eligibility runs through defined routes: the Help to Heat Group, Social Housing, LA Flex, In-Fill and Supplier Flex¹¹. Housing Benefit is a qualifying benefit under the Affordable Warmth route¹⁹. Because ECO4 is not a grant scheme in the ordinary sense, meeting an eligibility route does not guarantee funding: it is the energy provider's decision which retrofit projects to fund⁴. Funding for ECO4 is limited and was reported close to being fully allocated⁴.

The practical consequence is that a household on a low income in an inefficient property may find ECO4 covers more of the work, including insulation alongside heating, while a household outside the qualifying benefits that can afford the upfront cost of a heat pump will find the Boiler Upgrade Scheme more predictable. The two cannot be stacked, so the decision is made once per installation.

What the warranty covers

Warranty protection differs between the two routes, and the difference is worth understanding before work begins. Under ECO4 Flex, households are advised that if a contractor offers guarantees or warranties, they should obtain those documents after the installation²¹. The same guidance advises checking whether the installer is Gas Safe registered to work on gas boilers²¹.

A parliamentary debate on 17 June 2026 recorded that the cost of damage from faulty ECO4 and GBIS solid wall insulation can exceed the £20,000 limit covered by a valid guarantee²². That figure is a limit on guarantee cover, not a promise of payment, and it indicates the scale of remedial work that can arise when insulation is installed badly.

The Boiler Upgrade Scheme takes a different approach. Because all heating systems installed under the scheme must meet MCS standards approved and published by the Secretary of State, the installation falls within the MCS consumer protection framework rather than a scheme-specific guarantee². The grant itself is protected at the point of sale: installers must deduct the full BUS grant value from the quote before any payment is made by the property owner². That rule prevents a household paying the full price and waiting to be reimbursed.

One further protection sits in the ECO4 rules. Where a boiler or electric storage heater is replaced with an air source heat pump or district heating system and the new heating system is not of the same kind, the replacement does not count towards the ECO4 cap²³. That matters for households weighing whether a heat pump can be delivered within the scheme's limits.

What it costs, and what the grant actually covers

The Boiler Upgrade Scheme grant values are fixed and published. Air-to-water heat pumps and ground source heat pumps attract £7,500, and air-to-air heat pumps attract £2,500³. Exhaust air-to-water heat pumps are eligible for the £7,500 grant². From 21 July 2026, eligible off-gas grid properties with an air-to-water or ground source heat pump can apply for an uplifted grant of £9,000, and that uplifted value is in place until 31 March 2027². The uplift applies where the previous heating system being replaced was fuelled by oil or liquefied petroleum gas².

The grant history explains some of the confusion around figures. From 23 October 2023, the grant level for air source and ground source heat pumps increased from £5,000 and £6,000 respectively to £7,500²⁴. Older guidance still in circulation quotes the earlier £5,000 and £6,000 values²⁵. Where a household sees a lower figure, it is likely to predate October 2023.

The scheme's budget rules matter for timing. Unspent budget is not carried over to the next scheme year, so a grant voucher has to be used within its validity period²⁶. The BUS grant application has two stages, a voucher application and a voucher redemption application, and the application must be properly made within 120 days of the commissioning date². Voucher validity periods are three months for air-to-water and air-to-air heat pumps and six months for ground source heat pumps³.

ECO4 does not publish a grant amount in the same way, because it is not a grant scheme. The scheme is worth £4 billion overall, and the funding is limited and was reported close to being fully allocated⁴. Prices for the work itself are installer-quoted under both routes, and no published price list applies.

The company's status: where each scheme stands

The Boiler Upgrade Scheme is active and has been extended. As of 28 April 2026, the scheme has been extended to 2030, and the published closing date for applications is 30 December 2029 at 11:59pm². Applications properly made on or after 28 April 2026 fall under the current rules, and the uplifted grant for eligible off-gas grid properties applies to applications made on or after 21 July 2026². The scheme is open to domestic and small non-domestic properties²⁷.

ECO4 is in its final period. It will run until 31 December 2026, following a nine-month extension⁵. Government guidance refers to the ending of funding for the Energy Company Obligation scheme²⁸. Some councils already state that the grant is currently closed in their area⁶. Supplier notification deadlines under the scheme ran from August 2022 through to 1 February 2024, so the supplier obligations were set well before the current delivery period²⁹.

The two schemes therefore sit at different points in their lifecycles. A household applying for the Boiler Upgrade Scheme is applying to a scheme with a published end date in 2029 and an extension to 2030. A household pursuing ECO4 is working within a scheme that closes at the end of 2026, with limited funding and local variation in whether work is still being commissioned.

What it means for household energy independence

Both schemes move a household away from gas dependence, but they do so to different degrees and with different residual ties. A Boiler Upgrade Scheme heat pump replaces a fossil fuel or electric heating system and runs on electricity, so the household remains connected to the grid and to an electricity supplier². What changes is the fuel: the home no longer depends on the gas network for heat, and the grant is deducted from the quote upfront, so the household is not carrying the grant as a debt².

ECO4 delivers insulation alongside heating measures, which reduces the total energy a home needs rather than only changing the fuel it uses¹³. That is a deeper form of independence, because a well-insulated home is less exposed to price movements whatever the heat source. The trade-off is control: ECO4 is not a grant scheme, and it is the energy provider's decision which retrofit projects to fund⁴. A household cannot apply for ECO4 in the way it applies for a Boiler Upgrade Scheme voucher.

Neither scheme removes dependence on the grid or on a supplier. A heat pump needs electricity, and a household with a heat pump and no solar or battery remains exposed to electricity prices in the same way a gas household is exposed to gas prices. The schemes change which network a home depends on, and in ECO4's case how much energy it needs in the first place.

The schemes also differ in how long the support lasts. The Boiler Upgrade Scheme has a published closing date of 30 December 2029 and an extension to 2030². ECO4 closes on 31 December 2026⁵. For a household planning work over several years, that timing shapes which route is realistically available.

For the wider picture of how grants fit together, the full guide to home energy grants and schemes sets out the current landscape, and the Boiler Upgrade Scheme and ECO4 pages cover each route in detail. Households weighing the two directly can read the comparison of the Boiler Upgrade Scheme and ECO4, and those checking whether a heat pump qualifies under ECO4 can read ECO4 heat pump funding. The rule that prevents stacking is set out in ECO4 and other grants.