Can you combine energy grants? What stacks, what blocks and in what order

Yes, some energy grants can be combined, and some never can. The dividing line is simple once you know it: a single installation cannot be funded by more than one source of public money, and a property that has already had government funding or support for a heat pump or biomass boiler cannot claim it again¹. So one grant for the heat pump and a different grant for the insulation is usually fine; two grants for the same heat pump never is.

The two schemes most households are trying to pair are the Boiler Upgrade Scheme, which pays £7,500 toward a heat pump in Wales as promoted by the Welsh Government² and £5,000 toward a biomass boiler³, and ECO4, the supplier-funded scheme for low-income and vulnerable households. Those two cannot be blended: funding from the Boiler Upgrade Scheme and ECO cannot be blended for the same measure or included within an ECO4 project⁴. But other combinations are built to work together, most notably in Wales, where Green Homes Wales offers project cost top-up funding specifically designed to sit alongside a Boiler Upgrade Scheme grant⁵.

Order matters as much as eligibility. ECO4 closes on 31 December 2026⁶, and its rules require that any measure funded outside the scheme is installed either before the ECO4 project starts or after it is entirely finished⁷. Get the sequence wrong and funding can be lost. This page sets out what stacks, what blocks, and in what order to do the work.

The Boiler Upgrade Scheme: an upfront grant, not a loan

The Boiler Upgrade Scheme, formerly known as the Clean Heat Grant, provides upfront capital grants to help reduce the cost of installing heat pumps and biomass boilers in homes and non-domestic buildings¹⁰. It is a grant in the strict sense: money toward the cost of the work, with nothing to repay and no ongoing payments. That distinguishes it from loan-based schemes such as the old Green Deal, and it is why the scheme is the first port of call for most households considering a heat pump. The full application process is covered on how the Boiler Upgrade Scheme application works.

The application is installer-led. The installer applies for the grant on the property owner's behalf, discounts the grant from the invoice, applies to Ofgem for a grant voucher, and redeems the voucher after the installation is commissioned¹. The grant application is a two-stage process: a voucher application, then a voucher redemption application¹¹. Practically, this means the householder never handles the grant money, and the installer carries the administration.

The grant amounts are fixed by technology, not by the size of the job. Grants do not vary by the capacity of the installation¹¹, so a small flat and a large house get the same figure for the same technology. The approved grant categories notice lists £5,000¹³, which is the biomass boiler figure, and the scheme rules confirm £5,000 toward a biomass boiler³. For heat pumps, the Welsh Government promotes the scheme as £7,500 off a heat pump². The scheme had paid out over 25,000 grants by May 2024¹⁴.

The one-grant-per-property rule

The core limit is one grant per property³. That rule has three practical edges.

First, the installation cannot be funded by more than one source of public funds, and you cannot apply if you have already received government funding or support for a heat pump or biomass boiler¹. This is the rule that catches households out when they try to add a second government pot to a job that is already funded.

Second, a property is not eligible if a previous BUS grant has already been received for installing a heat pump or biomass boiler at the same address¹⁵. A grant is a one-time event for each property, not an annual entitlement.

Third, the exclusions are broad. You cannot get a grant for most new build properties, social housing, or a property that has already been given government funding or support for a heat pump or biomass boiler¹⁵. New build properties which the developer is still building are not eligible, though if you move into a finished new build with a fossil fuel boiler, you may be able to get a grant for a heat pump under the scheme¹⁵.

For a fuller picture of which homes and systems qualify, see Boiler Upgrade Scheme eligibility.

What the BUS actually funds

The 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 boilers¹⁶. Air-to-air heat pumps are explicitly included¹⁷. A consultation on consumer protection for home upgrade schemes describes the scheme's measures as heat pumps, biomass boilers and heat batteries in homes and non-domestic buildings¹⁸, and Ofgem's scheme page summarises the purpose as upfront grants to help reduce the cost of installing heat pumps and biomass boilers in homes and non-domestic buildings¹⁹.

Two conditions shape what the grant can be used for. The BUS-funded system must fully replace the property's existing fossil fuel or electric heating system, except where supplementary heating appliances are permitted¹⁷. And you cannot get a grant for a hybrid heat pump system, for example a combination of a gas boiler and an air source heat pump³. Biomass boilers funded through the scheme cannot be installed alongside supplementary heating appliances at all¹⁷.

The practical consequence for a household planning its energy independence is that the BUS buys a complete break with the old heating system, not a partial one. A hybrid arrangement that keeps the gas boiler as backup is outside the scheme, and the grant is sized to reward the full switch.

What stacks: measures that sit alongside the BUS rather than inside it

This is where combining grants genuinely works, provided the grants pay for different measures.

Energy efficiency funding does not block a BUS grant. If you have received separate funding for energy efficiency upgrades such as insulation, doors or windows, you can still apply for the Boiler Upgrade Scheme⁹. Insulation paid for by one scheme and a heat pump paid for by the BUS are separate measures, so the one-source-of-public-funds rule is not triggered. This matters because a heat pump performs best in a well-insulated home, and the two kinds of work are usually done in that order anyway.

Green Homes Wales is designed to stack. The project cost top-up funding available alongside a Boiler Upgrade Scheme grant can support costs of the heat pump technology, supply and fitting or labour, and associated pipework and radiator costs for heat pump projects⁵. This is the clearest example in the UK of a scheme built to sit on top of the BUS rather than compete with it: the BUS grant comes off the invoice, and the Welsh top-up helps with the remaining costs. See Green Homes Wales for the scheme's own terms.

ECO4 and GBIS do not stack. Funding for measures delivered under ECO4 must not be blended with funding from other government schemes or grants, including but not limited to Warm Home Discount, Boiler Upgrade Scheme, Social Housing Decarbonisation Fund and Home Upgrade Grant⁷. The Great British Insulation Scheme carries the same rule: funding for measures delivered under the Scheme cannot be blended with funding from other government schemes or grants, including the Boiler Upgrade Scheme and ECO4²⁰. Ofgem's ECO4 guidance states it directly:

Sequencing is the workaround. Where a home needs both an ECO4 package and work funded elsewhere, the rules allow it, but only in strict order: any measures outside ECO4 delivered to the same property must be installed either before the ECO4 retrofit project was started or after the entire project is complete and all measures have been installed⁷. A BUS-funded heat pump can therefore follow an ECO4 insulation project, or precede one, but the two cannot overlap in time.

ECO4: the other big scheme and how it interacts with the BUS

ECO4 is the supplier-funded obligation under which energy companies pay for insulation and heating measures in eligible homes. Where a household and property meet the criteria, support can include installing central heating where there is no boiler or radiators, replacing storage heaters or coal fires with gas central heating, replacing a non-condensing combi boiler with a modern combi boiler, or replacing a heat only boiler with a modern combi boiler²¹. The scheme's overall design is covered on the Energy Company Obligation and ECO4 eligibility.

The interaction with the BUS is asymmetric. A BUS heat pump grant cannot be blended into an ECO4 project⁴, and ECO4 measures cannot draw on other government funding⁷. But an ECO4 project at the same property does not permanently bar a later BUS application, provided the heat pump installation itself is not publicly funded twice and the ECO4 project is entirely finished first⁷. Ofgem's summary of ECO4 updates includes an updated paragraph on blended funding with the Boiler Upgrade Scheme, reflecting how often the two schemes meet²².

One restriction bites in the private rented sector. In general, the replacement, upgrade or repair of a boiler, central heating system or electric storage heater is not eligible in PRS properties²³, with the original delivery guidance stating the same position: the replacement, upgrade or repair of a boiler, central heating system or electric storage heater is not eligible in PRS, except where the replacement is first-time central heating, a renewable heating measure or a district heating connection²⁴. Landlords and tenants in this sector should read the position as: ECO4 is aimed at whole-home retrofit, not at boiler swaps.

The timetable is the sharpest constraint. ECO4 will run until 31 December 2026, following a nine-month extension²⁵, and installation extensions will not allow installation dates beyond the overall scheme deadline of 31 December 2026⁶. A project agreed in the final months of 2026 carries real completion risk, and because non-ECO4 work cannot overlap an ECO4 project, a delayed ECO4 installation can hold up a BUS application queued behind it.

Timetables and closing dates to plan around

The Boiler Upgrade Scheme opened for grant applications on 23 May 2022²⁶. The Carbon Budget Delivery Plan originally set the scheme to run until 31 March 2025²⁷, and the scheme has since been extended, with Ofgem able to issue BUS vouchers up to 31 December 2029¹⁷. The budget was increased with effect from April 2026, with the approval notice applying to England and Wales⁸.

Within that window there are dated changes to watch. Uplifted grants for eligible off-gas-grid properties apply to applications made on or after 21 July 2026¹⁶. Demand has been rising: the government reported the scheme having paid out over 25,000 grants by May 2024¹⁴, with increased applications following the grant uplift.

For households weighing the two schemes against each other, the comparison pages on BUS vs ECO4 and BUS or ECO4 for a heat pump work through the choice in detail.

England, Wales, Scotland and Northern Ireland: what differs

The Boiler Upgrade Scheme applies to England and Wales⁸, a territorial extent confirmed again in the 2025 evaluation of the scheme²⁸. Within England and Wales the rules are the same, but Wales adds the Green Homes Wales top-up, which is explicitly designed to sit alongside a BUS grant and cover heat pump technology, labour, pipework and radiator costs⁵. A Welsh household therefore has a stacking opportunity that an English household on the same income does not, and the Welsh Government actively promotes the £7,500 heat pump grant².

Scotland sits outside the BUS entirely. Scottish households planning a heat pump look instead to the Home Energy Scotland grant and loan, where grant and loan elements can be combined in ways the BUS does not allow, and the comparison between grant and loan is a live decision rather than a technicality. The BUS rule that one installation cannot draw on two public sources¹ is the England-and-Wales rule; Scottish schemes have their own terms.

Northern Ireland also sits outside the BUS. Households there rely on the Northern Ireland schemes, including the Affordable Warmth Scheme and NISEP, which are structured separately from GB-wide schemes. The BUS statistics describe the scheme as providing upfront capital grants to support the installation of heat pumps and biomass boilers in homes and non-domestic buildings²⁹, and that support reaches homes in England and Wales only.

The scheme's own scope is worth noting for non-domestic readers too: the grant can be used to replace a heating system in your home or a building used for your business³¹, so a farm business or small commercial premises in England or Wales can access the same grant route.

What this means for a household's independence

A grant combination that works, done in the right order, reduces what a household must find from its own pocket and speeds up the move away from fossil heating. The BUS grant alone leaves a substantial balance to pay, since grants do not vary with the size of the installation¹¹; the Welsh top-up narrows that gap⁵. What no grant removes is the dependence that remains: on an MCS-certified installer to make the application¹, on Ofgem to issue and redeem the voucher¹², and on the scheme's own deadlines, which for ECO4 are now close⁶. A household that sequences its work around those dependencies keeps its funding; one that lets two schemes collide on the same measure at the same time can lose both.