Boiler Upgrade Scheme for business: limits, rates and who applies

If you run a shop, small office, school, care home, hotel, church hall or charity building, you may be asking whether the boiler upgrade scheme business route is open to you. The Boiler Upgrade Scheme (BUS) is usually described as a home grant, but it is not domestic only. It covers heat pumps and biomass boilers in homes and in non-domestic buildings in England and Wales.

This guide sets out what the sources say, where they stop, and what you should confirm before you rely on the grant. It sits alongside our wider overview of commercial heat pump grants. We are an independent information site, not an installer, and every figure below was checked on 20 October 2026.

Do non-domestic buildings qualify for the Boiler Upgrade Scheme?

Yes, in principle. Ofgem, which administers BUS, states that the scheme supports heat pumps and biomass boilers in domestic and non-domestic buildings across England and Wales. A June 2025 Parliamentary written answer went further and confirmed that the scheme continues to give grants of up to £7,500 to small non-domestic property owners.

What the sources do not give is a definition of which non-domestic properties qualify. Ofgem's scheme page does not list building types, floor areas or business sizes. That gap matters, because a small shop and a large hospital are both non-domestic, but the scheme's size limit means they will not be treated the same way in practice.

Treat it as a route that is open on paper and needs confirming for your specific building. Two parties can confirm it: an MCS certified installer, who deals with the scheme rules every day, or the Department for Energy Security and Net Zero (DESNZ), which you can email at boilerupgradescheme@energysecurity.gov.uk. Do this before you sign anything, not after.

The 45 kWth limit and shared ground loops

BUS is capped by system size. A single installation can be no larger than 45 kWth, which is a measure of thermal output. This is the single most important filter for a business reader, because it decides whether the scheme fits your building at all.

Many small commercial buildings sit comfortably below that figure. Larger sites, such as big schools, hotels, leisure centres or multi-tenant offices with a large heat load, may need a system that exceeds it. If your design heat load is above the limit, a single BUS-funded installation cannot cover the whole requirement.

There is one stated exception. A shared ground loop can be up to 300 kWth. A shared ground loop is a single ground heat exchanger that serves several separate heat pumps. The source wording is brief, so ask the installer how the scheme would treat your proposed layout, and ask them to confirm it in writing against the current Ofgem guidance rather than assuming it.

The sensible first step is to get the building's heat load calculated properly, then compare it to 45 kWth. If you are weighing larger plant, our page on commercial air-source heat pumps covers the technology side.

The £7,500 and £9,000 grant rates

The standard BUS grant is £7,500 for an air-to-water, ground-source or water-source heat pump. Biomass boilers receive £5,000. A £2,500 grant for air-to-air heat pumps exists, but it is for residential properties only, so it does not apply to a business building.

A higher rate of £9,000 is available for an air-to-water or ground-source heat pump in an eligible off-gas-grid property. Under the sources checked, new applications at that rate opened from 21 July 2026, and the rate is available to 31 March 2027. Treat 31 March 2027 as the date to plan around, and check Ofgem for any change before you apply.

Whether your building counts as an eligible off-gas-grid property is a question to put to the installer or DESNZ. Do not assume a rural location or an oil boiler is enough; ask for the eligibility test to be applied to your address.

Be realistic about what the grant is. For a larger commercial system, a fixed contribution of this kind is a modest part of the total spend. It reduces the net cost, but it does not remove the need for a funded project. Our cost guide explains what drives the overall figure so you can set the grant in context.

Who applies, and who must own the property

You do not apply for BUS yourself. The installer must be MCS certified, and the installer applies for the voucher on the owner's behalf. This is a common point of confusion: the grant is claimed through the installer, and the customer's role is to agree the work and confirm ownership.

The applicant must own the property. Landlords can apply, which matters if you let out commercial space. If you are a tenant, you generally cannot be the applicant, so you would need the owner or landlord to take the lead, or to give permission and support for the project.

If a building has several owners or a split ownership structure, sort out who the applicant will be early. It is easier to settle this before the quote stage than after an installation has been planned around a particular name.

The 120-day rule

The system must have been commissioned no more than 120 days before an application is properly made. In plain terms, the clock runs from commissioning, and the application has to be in properly and in time.

The practical lessons are simple. Do not let the paperwork lag behind the installation. Agree with the installer, in advance, who submits the application and by when. Keep the commissioning date and supporting documents together so that nothing needs to be chased once the system is live.

If the installation is staged or phased, ask the installer how the rule applies to each part, and get the answer in writing.

What BUS does not cover

BUS is a fixed grant for systems up to 45 kWth, or up to 300 kWth for a shared ground loop. It does not fund a larger single system. A big commercial building with a heat load well above that size will not find BUS covering its main plant.

For larger schemes, the funding picture is different and mostly closed or competitive. The Green Heat Network Fund supports new and retrofitted heat networks in England and Wales, but on the date checked no round was open: Round 11 closed on 2 May 2026 and Round 12 closed at 11.59pm on 25 September 2026, and the gov.uk page lists no later round. Watch gov.uk for the next one.

Two other schemes are not available. The Industrial Energy Transformation Fund is closed, with no successor fund planned. The Public Sector Decarbonisation Scheme closed to new applications in November 2024, and government has committed no further investment beyond projects already awarded. Do not build a business case on either of them.

For the full picture of what is open and closed, see our guide to commercial heat pump grants.

How BUS combines with capital allowances

A heat pump is generally plant and machinery, so a business paying tax may be able to claim relief on the cost it funds itself. The Annual Investment Allowance, which is £1 million a year, and other capital allowances are the reliefs to ask about.

The key point is that relief applies to the cost the business pays for. A grant reduces the qualifying spend, so you should model the tax relief on the net amount after the BUS grant, not on the gross quote. Do not assume the grant and the allowance both apply to the same pound of spending.

Treat this as a planning prompt, not tax advice. Take the quote, the grant amount and the ownership structure to your accountant, who can confirm what you can claim and in which year.

The scheme end date question

There is no scheme end date on Ofgem's BUS page in the sources we checked. We have not found one, and we are not going to guess. What the sources do give is the 31 March 2027 date for the higher £9,000 off-gas-grid rate.

Those are two different things. The higher rate has a stated date. The scheme as a whole has no date given. Do not read the absence of an end date as a promise that BUS will continue, and do not read the 2027 date as the end of the whole scheme.

The sensible approach is to check the Ofgem BUS page yourself before you commit, and again before the application is submitted. Funding rules change, and an installer who has recently submitted applications will usually know of any recent change.

Step by step: how to approach a BUS application

Work through the following in order. It keeps you from paying for design work on a project that turns out not to qualify.

• Confirm the building is in England or Wales and that you or your landlord own it.
• Estimate the heat load and compare it to 45 kWth.
• Ask an MCS certified installer, or DESNZ, to confirm that the building counts as an eligible non-domestic property.
• Check whether the property is eligible for the £9,000 off-gas-grid rate.
• Agree who submits the voucher application and who is the applicant.
• Note the commissioning date and plan to apply well inside 120 days.
• Check the Ofgem BUS page for the current rules and end date before you sign.
• Speak to your accountant about capital allowances on the net cost.

What to ask an installer

Use these questions when you collect quotes. They are reader instructions, not promises from anyone, and the answers should be in writing.

• Are you MCS certified, and can you show the certificate?
• Will you apply for the BUS voucher on the owner's behalf, and when?
• Does my building qualify as a non-domestic property under BUS?
• What is the design heat load, and is the system under 45 kWth?
• If the system is larger, how would a shared ground loop or split installations be treated?
• Is the property eligible for the £9,000 off-gas-grid rate?
• How will the 120-day rule be managed on this project?
• What happens to the quote if the grant is refused or changes?

If BUS does not fit your building

If the building is too large, outside England and Wales, or not eligible, the route changes. Larger sites often need a project-financed approach, supported by tax relief and, where a heat network is involved, by the Green Heat Network Fund when a new round opens. Existing networks may be able to use the Heat Network Efficiency Scheme, which part-funds performance improvements and optimisation studies; check gov.uk for the dates of the current round.

Whatever the route, start with the heat load and the building's use. Our cost guide and our overview of commercial heat pump grants are the next pages to read. If you want to talk it through, send an enquiry and we reply by email.

Frequently asked questions

Can a business get a Boiler Upgrade Scheme grant?

Yes, in principle. Ofgem states that BUS supports heat pumps and biomass boilers in homes and non-domestic buildings in England and Wales. A June 2025 Parliamentary answer says it continues to give grants of up to £7,500 to small non-domestic property owners. Ofgem does not say which non-domestic properties qualify, so confirm eligibility with an MCS installer or DESNZ.

What is the maximum system size for BUS?

A single installation is limited to 45 kWth. A shared ground loop can be up to 300 kWth. If your building's heat load is above 45 kWth, a single BUS-funded system cannot cover it, so get the heat load calculated first and ask the installer how the scheme would treat your layout.

How much is the grant for a business heat pump?

The grant is £7,500 for an air-to-water, ground-source or water-source heat pump. An eligible off-gas-grid property can receive £9,000 for an air-to-water or ground-source heat pump, with new applications from 21 July 2026 and the rate available to 31 March 2027. The £2,500 air-to-air grant is residential only.

Who applies for the grant, the business or the installer?

The installer applies for the voucher on the owner's behalf, and the installer must be MCS certified. The applicant must own the property, and landlords can apply. A tenant generally needs the owner involved. Agree early who the applicant is and who submits the application.

What is the 120-day rule?

The system must be commissioned no more than 120 days before an application is properly made. The clock runs from commissioning, so the application must be in time. Agree with the installer, before work starts, who submits it and by when, and keep the commissioning documents together.

When does the Boiler Upgrade Scheme end?

Ofgem's page, as checked on 20 October 2026, does not state a scheme end date. The only date given is 31 March 2027 for the higher £9,000 off-gas-grid rate. Check the Ofgem BUS page yourself before you commit and again before the application is submitted.