Ofgem’s Boiler Upgrade Scheme guidance states that hybrid heat pump systems, meaning a combination of a fossil fuel boiler and a heat pump such as an air source heat pump, are not eligible for the scheme, whether the fossil fuel boiler is a separate retrofit unit or integrated into the same system as the heat pump.

Why hybrids are excluded

The Boiler Upgrade Scheme, administered by Ofgem, provides a grant toward replacing a fossil fuel or electric heating system with a low-carbon alternative, and its guidance is explicit that a hybrid arrangement combining a heat pump with a fossil fuel boiler does not qualify. This applies regardless of the specific configuration: a heat pump installed alongside a separate existing or new fossil fuel boiler, sometimes called a retrofit hybrid, is excluded, and so is a system with an integrated fossil fuel boiler component built into the same unit as the heat pump.

What does qualify

The scheme instead funds fully electric or biomass-based systems: air-to-water heat pumps, air-to-air heat pumps, ground source heat pumps, including water source heat pumps and those on a shared ground loop, and biomass boilers, the last of these limited to rural, off-gas-grid properties. What unites all of these eligible categories is the absence of any fossil fuel component within the funded system itself.

The grant amounts

Grant values differ by technology: £7,500 is available toward an air-to-water heat pump or a ground source heat pump, £2,500 toward an air-to-air heat pump, and £5,000 toward a biomass boiler. A higher rate of £9,000 applies to air-to-water or ground source heat pumps installed at off-gas-grid properties between July 2026 and March 2027. None of these figures apply to any part of a hybrid system, since the scheme’s eligibility rules exclude the whole arrangement, not just the fossil fuel boiler component within it.

Why a fossil fuel boiler in the system disqualifies it

The scheme’s underlying purpose is to support a genuine switch away from fossil fuel heating, so a system that keeps a fossil fuel boiler in place, even one working alongside an efficient heat pump and only handling a smaller share of the home’s heat demand, does not meet that objective in the way the scheme defines it. This holds even where the heat pump component of a hybrid system would, on its own specification, otherwise meet the scheme’s technical standards, because it is the presence of the fossil fuel boiler within the overall system, not the heat pump’s own performance, that disqualifies it.

What this means if you’re considering a hybrid

Anyone weighing up a hybrid system against a fully electric heat pump needs to factor in that the hybrid option will not attract Boiler Upgrade Scheme funding, which changes the relative upfront cost comparison significantly compared with an eligible fully electric or biomass system of similar capability. A hybrid system may still suit a particular property for other reasons, such as backup heating capacity during extreme cold, but that decision has to be made without the grant available to the fully qualifying alternatives.

Other conditions that still apply

Beyond the technology itself, a qualifying system under the scheme must be replacing an existing fossil fuel or electric heating system, must not have been commissioned more than 120 days before the application, and has to meet the scheme’s technical efficiency requirements, which an installer delivering an eligible system should be able to confirm and document as part of the application.

Checking before committing to a design

Because the exclusion applies to the system as a whole rather than to any single component, it is worth confirming a proposed heating design’s eligibility with the installer, and ideally checking the scheme’s own current guidance, before committing to a specific system design, rather than assuming a heat pump-led proposal automatically qualifies simply because a heat pump is the main component being installed. An installer proposing a hybrid design for genuine technical reasons, such as an older property with high peak heat demand, should be able to explain clearly that the grant will not apply to that particular configuration.

FAQs

Can I get a Boiler Upgrade Scheme grant for a heat pump if I keep my old gas boiler as backup?

No. A hybrid arrangement combining a heat pump with a fossil fuel boiler, in any configuration, is explicitly excluded from the scheme.

Does it matter if the fossil fuel boiler is a separate unit rather than built into the heat pump system?

No. The exclusion applies whether the fossil fuel boiler is a separate retrofit unit or integrated into the same system as the heat pump.

What grant is available for a fully qualifying air-to-water heat pump?

£7,500, the same rate that applies to a ground source heat pump, rising to £9,000 for off-gas-grid properties between July 2026 and March 2027.

Are biomass boilers eligible under the scheme?

Yes, at £5,000, but only for rural, off-gas-grid properties.

Bottom line

A hybrid system that pairs a heat pump with a fossil fuel boiler, however the two are configured, does not qualify for the Boiler Upgrade Scheme’s grant under Ofgem’s guidance; only fully electric heat pumps and, for off-gas-grid rural properties, biomass boilers are eligible, at grant amounts ranging from £2,500 to £9,000 depending on the technology and location. This is general information, not advice on a specific property; an accredited installer can confirm whether a proposed system meets the scheme’s current technical requirements.

Sources

This guide draws on the following primary sources, current as of 22 September 2026:

• Ofgem, “Boiler Upgrade Scheme (BUS) – Property owners”

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Best Boiler Deals is an independent guide. We may earn a fee from some links; this never affects what we write. This article is general information, not regulated advice on any specific installation — always confirm the details with a Gas Safe registered engineer.