Boiler Upgrade Scheme (BUS)

What to know first

These are the main points to understand before you compare Boiler Upgrade Scheme options.

Could BUS support your heating upgrade?

BUS may reduce the upfront cost where the property, existing heating and proposed system meet the current rules. Only a property-specific assessment can establish design, performance, permissions or suitability, and Ofgem confirms eligibility only after a complete installer application.

Introduction

The Boiler Upgrade Scheme (BUS) is a government grant scheme for properties in England and Wales. It helps with the upfront cost of installing certain heat pumps and, in limited circumstances, biomass boilers. The scheme is administered by Ofgem and is led by the installer rather than the property owner.

For applications properly made on or after 21 July 2026, the headline grants are £7,500 for air-to-water and ground-source heat pumps, £2,500 for air-to-air heat pumps, and £5,000 for eligible biomass boilers. A temporary £9,000 grant is available for certain off-gas-grid properties replacing oil or LPG heating with an air-to-water or ground-source heat pump. That uplift is scheduled to end on 31 March 2027.

This guide explains the current scheme in plain English. It is general information, not confirmation that a property or installation qualifies. Grant rules, annual budgets, technical standards and property evidence can change, and an MCS-certified installer must assess the proposed installation before Ofgem decides an application.

What BUS is - and what it is not

BUS is mainly experienced as a discount in an installer quote and final invoice. Ofgem pays the grant to the installer after a successful redemption application; the property owner does not receive the grant as cash. The installer must show the deduction upfront rather than asking the owner to pay the grant-funded amount and reclaim it later.

BUS is not a general home-improvement fund. It does not automatically pay for every change a property may need, and it does not guarantee that the grant will cover the difference between a low-carbon system and a boiler replacement. It also does not replace planning, building-control, landlord, freeholder, electrical or environmental checks that may apply.

The standard route is to apply before installation. Since the 2026 rule changes, a retrospective application may be possible in some cases if it is properly made within 120 days of commissioning. That route carries extra risk because funding is not guaranteed after work has been completed.

BUS at a glance

Who is this guide for?

This guide is for homeowners, landlords and owners of small non-domestic properties who want to understand BUS before requesting quotes. It is also useful if you are replacing gas, oil, LPG or direct electric heating and want to compare a heat pump or eligible biomass boiler with other options.

Tenants can use the guide to understand the process, but the property owner normally needs to approve the work and provide the scheme consent. Owners of flats, listed buildings, leasehold homes, shared ground-loop projects and self-builds may need additional checks or evidence.

What this guide covers

The guide explains:

• why the scheme was introduced and how it fits into heat decarbonisation

• the main property, ownership and existing-heating eligibility rules

• which heating systems are supported and how the categories differ

• current grant amounts, voucher periods and what the grant may cover

• the installer-led application, consent, installation and redemption process

• what MCS certification and consumer-code membership do and do not mean

• how to budget for equipment, radiators, cylinders, electrics and groundworks

• the factors that affect running costs, performance and carbon impact

• the benefits, limitations and practical checks to consider before proceeding

• how BUS may interact with other public support and devolved schemes

Why the scheme was introduced

Heating buildings is a major source of UK energy demand and carbon emissions. Many homes still use gas, oil or LPG boilers, while some use direct electric heating. Moving to lower-carbon heating can require more upfront investment than replacing a boiler with a similar model, so cost is one of the main barriers.

What problem is BUS trying to solve?

BUS narrows part of the upfront price gap. It gives installers a fixed grant to deduct from an eligible project, making it easier for property owners to compare the amount they would still need to pay. The grant does not make every project affordable, but it can materially change the starting cost.

The scheme also supports market development. More installations create demand for trained installers, system design, equipment, aftercare and consumer protection. Government policy has extended BUS to 2030 and increased its planned annual budgets, although the amount available for vouchers remains subject to confirmed allocations and scheme rules.

How BUS fits into wider heating policy

BUS is one part of wider policy to reduce emissions from buildings and expand the market for low-carbon heating. It is a financial incentive, not a rule requiring every property owner to replace a boiler by a particular date. The scheme reduces part of the purchase price where the current eligibility conditions are met; it does not remove the need to compare technologies or decide when replacement makes sense.

Its market role operates at several points. A visible grant can make low-carbon heating easier to consider at quote stage. Linking funded work to current certification and consumer-protection requirements can support more consistent processes. Higher installation volumes can also give installers and suppliers greater confidence to invest in training, products and aftercare. None of these aims guarantees a lower quote or a better result for an individual project.

The carbon case depends on the system in practice as well as the technology label. Relevant factors include the heating system being replaced, seasonal efficiency, flow temperature, controls, electricity generation and how well the building retains heat. BUS eligibility confirms that a project meets scheme conditions; it does not prove a particular carbon saving or running-cost outcome.

Why design and building readiness still matter

A grant can reduce price, but it cannot correct poor design. Heat pumps usually work best when heat loss, emitters, flow temperatures, hot-water demand and controls are considered together. Some properties need insulation, larger radiators, pipework changes, a hot-water cylinder or electrical work. Others may need fewer changes.

This is why BUS is tied to MCS certification and technical requirements. The framework is intended to support consistent design and documentation, but certification is not a guarantee of comfort, savings or workmanship. The property-specific proposal and the contract still matter.

What the scheme means for consumers

The scheme gives consumers another option at the point when a heating system is being replaced or a planned upgrade is being considered. It can support a move away from on-site fossil-fuel use, but the right choice still depends on the building, current heating, available space, budget, local permissions and how the system will be used.

Ofgem reported that 90,115 BUS grants had been paid from the scheme launch to 31 July 2026. Of these, 88,092 (97.8%) were for air-to-water heat pumps, while no air-to-air grants had yet been paid. This shows the scheme is established, but aggregate figures do not predict the performance or cost of an individual installation.

Who is eligible

BUS eligibility is assessed from the property, its ownership, the heating system being replaced, the proposed technology and the evidence submitted. The scheme is not means-tested, but that does not make approval automatic. Ofgem confirms eligibility only after the installer submits a properly made application.

The main property and ownership tests

At a high level, BUS is intended for existing residential and small non-residential buildings in England and Wales. The applicant installer acts for the property owner. One owner can usually give consent for a jointly owned property if they confirm they have authority to act for the other owners. Organisations must use an individual who is legally authorised to represent them.

Both homes and non-residential properties can qualify, subject to the wider rules. Air-to-air heat pumps are an exception: they are eligible only in residential buildings. Churches, park homes and other less common property types may qualify where the detailed requirements are met.

The person benefiting from BUS must become the legal owner of the installed heat pump or biomass boiler. Finance arrangements that leave ownership with an installer or finance company are not eligible. Ask how ownership works before signing a credit or rental agreement.

Which existing heating systems can be replaced?

The scheme is mainly aimed at replacing fossil-fuel heating, such as gas, oil or LPG, and direct electric heating that is not already a heat pump. An existing fossil-fuel system must be fully replaced. You cannot retain a gas, oil or other fossil-fuel boiler alongside the BUS-funded installation.

Some non-fossil supplementary appliances may be allowed with a BUS-funded heat pump. The heat pump must still meet the relevant capacity and system requirements, so this is a design question for the installer rather than a general permission to keep any backup system.

Do you need a valid EPC?

A valid Energy Performance Certificate is no longer a standing eligibility requirement for applications properly made on or after 28 April 2026. Where a valid EPC exists, the installer includes its reference number. It can still be useful because it records basic property information and may help the installer prepare the application.

Where there is no valid EPC, the installer must provide alternative evidence. Ofgem guidance gives examples such as a recent utility bill or fuel receipt, photographs of the existing heating system and an expired EPC where one is available. The exact evidence depends on the application.

Common situations that are not eligible

The most common exclusions include:

• social housing, including shared-ownership properties treated as social housing

• most new-build properties, except certain qualifying self-builds

• a property that already has a heat pump as its existing main heating system

• public funding already used for the same low-carbon heating installation

• a fossil-fuel hybrid arrangement that keeps a boiler with the funded heat pump

• finance where the property owner never becomes legal owner of the equipment

This is not a complete list. Renovations, conversions, mixed ownership, shared land and unusual heating arrangements may need closer evidence checks.

Special cases: self-build properties

Certain self-build homes can qualify even though most new builds cannot. The definition is evidence-based: the home must have been built mainly using the labour or resources of its first owner, it must not have been owned by a business or other non-individual while it was being built, and it cannot form part of an excluded property development.

Self-build applicants should raise this at the first installer conversation. Title records, invoices, contracts, planning documents and other evidence may be needed. Qualifying self-builds may receive the standard £7,500 heat-pump grant, but they are not eligible for the temporary £9,000 off-gas uplift. Biomass boilers are not supported for self-build properties.

Extra rules for off-gas and biomass applications

The temporary £9,000 grant applies only to certain off-gas-grid properties replacing oil or LPG with an air-to-water or ground-source heat pump. For this uplift, Ofgem uses a specific off-gas definition. A capped or clamped mains-gas meter point can still count as mains gas, and a property attached to a heat network does not meet the uplift definition.

Biomass support is narrower. The property must be off the gas grid and in a rural location, the boiler must meet emissions and fuel requirements, and the installation must provide the required space and hot-water heating. Local air-quality controls, fuel storage, deliveries and servicing also need consideration.

A quick sense check before requesting quotes

It may be worth discussing BUS with an installer where most of the following are true:

• you own the property or can legally act for the owner

• the property is in England or Wales

• the existing main heating is fossil fuel or qualifying direct electric

• you are prepared to remove any existing fossil-fuel heating system

• the proposed technology is one of the current BUS categories

• you can provide an EPC reference or help gather alternative evidence

• you understand the grant may leave a substantial balance to pay

• you can complete the project within the relevant voucher period

A failed sense check does not always mean the answer is no. It means the installer may need more evidence or a different system proposal. Ofgem, not Clearwise or an online form, makes the scheme decision.

Eligible heating systems explained

The 2026 rules recognise four main technology categories. Each has different uses, grant values and property constraints. The category tells you what may be funded; it does not establish that a particular model or design will work in your building.

How heat pumps work in practical terms

A heat pump uses electricity to move heat from air, ground or water into a building. It can deliver more heat energy than the electrical energy it consumes because most of the heat is transferred rather than created by resistance heating. Real-world performance depends on outside conditions, heat loss, flow temperature, controls, emitter sizing, hot-water demand and installation quality.

Air-to-water and ground-source systems usually connect to a wet heating system and can provide stored hot water. Air-to-air systems deliver warm air through indoor units and normally need a separate way to provide domestic hot water.

Air-to-water heat pumps

Air-to-water heat pumps take heat from outside air and transfer it to water for radiators, underfloor heating and a hot-water cylinder. They are the most common BUS category and carry a £7,500 grant under the current standard rules. Eligible off-gas properties replacing oil or LPG may receive £9,000 while the temporary uplift is open.

Exhaust air-to-water heat pumps can also qualify for the £7,500 grant where they meet the same BUS and MCS requirements as other air-to-water systems. Exhaust air-to-air systems are not currently eligible because they cannot currently be MCS certified.

The main property checks are outdoor-unit siting, noise, heat loss, radiator and pipework capacity, cylinder space, electrical supply and the proposed flow temperature. Some existing homes need significant changes; others can use much of the current system.

Air-to-air heat pumps

Air-to-air heat pumps transfer heat from outside air and distribute it through indoor fan units. They can be useful where a wet radiator system is absent or where room-by-room warm-air heating is practical. Some can also provide cooling, although a cooling-only installation is not the purpose of BUS.

The current grant is £2,500 and is available only for residential properties. Air-to-air systems do not normally provide domestic hot water, so the overall proposal must address hot water separately. Ducting or several indoor units may affect layout, appearance and noise.

Ground-source and water-source heat pumps

Ground-source heat pumps collect heat through buried loops or boreholes. Water-source systems use a suitable body of water and are treated within the ground-source category. The ground or water source can provide more stable temperatures than outside air, but the installation may involve surveys, permissions, excavation, drilling and reinstatement.

The standard grant is £7,500, with the temporary £9,000 uplift for qualifying off-gas properties replacing oil or LPG. Shared ground loops can be eligible, but each property normally needs its own voucher and consent. The technical and legal arrangements should be clear before anyone commits to communal infrastructure.

Biomass boilers

A biomass boiler burns an eligible solid biomass fuel, often pellets, to provide space heating and hot water. The current grant is £5,000, but the category is limited to rural, off-gas-grid properties and is subject to air-quality, emissions, fuel and system requirements. Biomass stoves are not eligible. A BUS-funded biomass boiler must meet the property’s full space-heating and hot-water demand on its own and cannot be installed alongside supplementary heating appliances under the scheme.

Biomass requires more ongoing handling than a heat pump. Fuel must be bought, delivered and stored; ash needs managing; and regular servicing is important. Combustion emissions also mean local smoke-control and air-quality restrictions need careful checking.

Technology comparison

Capacity, hybrid and supplementary-system rules

BUS sets capacity and configuration rules. Current Ofgem installer guidance gives maximum limits of 45 kWth for an individual heat-pump system, 70 kWth for a multi-heat-pump system and 300 kWth in total for a shared ground loop, with each connected heat pump no more than 45 kWth. An individual biomass boiler is limited to 45 kWth.

Air-to-water and ground-source heat pumps must also achieve an in-situ SCOP of at least 2.8 using the approved MCS calculation. This is a scheme threshold, not a promise of household performance or bills.

These are scheme limits, not sizing recommendations. An installer must calculate the property heat demand and show that the proposal meets the technical rules. A system should never be selected simply because it fits below a grant threshold.

Fossil-fuel hybrids are not eligible. A hybrid-capable heat pump may qualify only when installed without a fossil-fuel appliance. Certain non-fossil supplementary appliances, such as direct electric heating or thermal storage, can be used in some configurations, but the funded heat pump must still meet the applicable space-heating requirement.

What BUS does not fund as a separate grant

Solar PV, solar thermal, standalone batteries and heat batteries do not currently have their own BUS grant category. They may be installed separately or, where the technical rules allow, form part of a wider energy system. BUS funds the eligible heating plant, not every technology connected to the property.

Grant amounts and what is covered

BUS uses fixed voucher values rather than paying a percentage of the final bill. The value depends on the technology and, for the temporary uplift, the existing fuel and off-gas status. The installer must show the grant as an upfront deduction in both the quote and the final invoice.

Current grant values and voucher periods

A voucher period starts when the voucher is issued. Air-to-water, air-to-air and biomass vouchers normally last three months; ground-source vouchers last six months. If it becomes clear the project cannot be completed in time, the installer must withdraw the voucher before making a new application. If it has already expired, a new application is needed without withdrawing the expired application. You must consent again, and replacement funding is not guaranteed.

What can sit within the funded installation?

The eligible plant can include the main heat pump or biomass boiler and necessary ancillary equipment. Depending on the design, this may include pipework, controls, valves, heat emitters, cylinders, buffer vessels and other equipment needed to install and commission the eligible system.

That does not mean every building cost is paid by BUS. The voucher is fixed, so the property owner pays the balance. Decorative repairs, extensive building work, unusual access, planning fees, major electrical upgrades, asbestos management, structural work, ground reinstatement and optional extras can increase the final cost.

What to budget for beyond the grant

Funding and ownership rules

The same installation cannot normally receive BUS and another public grant for the same low-carbon heating plant. Separate support for insulation or another distinct measure may be possible, but each scheme has its own interaction rules. Keep funding offers and written approvals so the installer can check for double funding.

You must become the legal owner of the installed equipment. Hire-purchase, conditional-sale and consumer-hire arrangements that leave ownership with a third party are not eligible under current Ofgem guidance. Other loans or payment plans may be possible where ownership passes to the property owner, but the contract needs checking.

Annual budgets and availability

Government sets an annual scheme budget and Ofgem cannot issue new vouchers once the relevant budget threshold is reached. A queue may operate if funding is temporarily unavailable. An already issued, valid voucher can still be paid after successful redemption, but submitting a form or receiving a quote does not reserve budget.

The application process

BUS is designed so the installer handles most of the administration. The property owner still has important decisions and must give consent directly to Ofgem. Understanding the sequence helps you avoid signing a contract before the scope, evidence and funding position are clear.

Step 1: prepare the property information

Gather the address, ownership details, current heating type, any EPC reference, recent energy or fuel evidence and information about unusual property circumstances. Tell the installer early if the home is a self-build, leasehold, listed, jointly owned, off the gas grid, connected to a heat network or used partly for business.

Step 2: find an eligible installer

Choose an installer that is MCS certified for the proposed technology and able to take part in BUS. Check the current MCS register rather than relying only on a logo or advert. For consumer work, the installer must also meet the applicable approved consumer-code requirements.

Where possible, compare more than one quote. Ask each installer to explain the system design, assumptions, included work, grant deduction, payment stages, warranty, aftercare and what happens if Ofgem rejects or delays the application.

Step 3: survey, heat-loss work and design

The installer should assess the property and proposed technology. For heat pumps, this normally includes room-by-room heat loss, emitter and pipework checks, flow-temperature assumptions, hot-water demand, controls, electrical needs, outdoor siting and noise. Ground-source and biomass projects need additional site-specific work.

A questionnaire or remote estimate cannot replace these checks. Ask for the important design outputs in writing and make sure any recommended insulation, radiator, cylinder or electrical work is included or clearly excluded.

Step 4: agree an itemised quote

The quote should show the gross project cost, the applicable BUS deduction and the amount you would pay. It should identify the equipment, installation scope, provisional items, payment timetable, cancellation rights, expected programme and responsibility for permissions and making good.

Do not compare only the post-grant total. A cheaper quote can omit work needed later, while a higher quote may include emitter changes, electrical upgrades, ground reinstatement or a stronger aftercare package.

Step 5: the installer submits the voucher application

Once you decide to proceed, the installer submits the application to Ofgem. It includes the installation address, proposed system, existing heating, quote details, grant deduction, gas-grid status and an EPC reference where one exists. The installer supplies the evidence; the property owner supports them where documents or clarification are needed.

Step 6: give consent and complete identity checks

Ofgem contacts the property owner directly using a secure government-notification email. You confirm the application details, ownership, grant deduction, public-funding position and other declarations. Current guidance says consent must normally be provided within 14 days of the email or the application may be rejected and need resubmitting.

Ofgem may use an identity-verification service or request documents. Check the address and voucher details carefully before consenting. Consent allows the installer to apply; it does not replace or amend the installation contract.

Step 7: voucher decision and installation

Ofgem assesses whether the application is properly made and meets the scheme rules. If approved, it issues the voucher to the installer. The project must then be installed and commissioned within the voucher period: three months for air-to-water, air-to-air and biomass, or six months for ground source.

The installer commissions the system, provides the required handover documents and obtains the MCS certificate. Keep the final design, commissioning records, warranties, consumer-code documents, invoice and proof of payment. Ofgem may contact you or arrange an audit.

Step 8: redemption and payment

After commissioning, the installer submits a redemption application. Ofgem checks the remaining evidence and, if successful, pays the grant to the installer. The property owner has already received the benefit through the deduction shown in the quote and invoice; there is no separate payment to claim.

Can an installer apply after the work is complete?

In some cases, an installer can make a retrospective voucher application after commissioning if it is properly made within 120 days. This is not the same as a guaranteed rebate. Ofgem warns that retrospective applications carry additional risk because an installation can be completed and still fail the funding rules.

Before agreeing to start without a voucher, ask who bears the cost if the application fails, what evidence has already been checked and whether the contract makes the risk clear. The safer consumer journey is usually to wait for the voucher unless there is a well-understood reason not to.

What happens if details change or the voucher expires?

Tell the installer promptly if the owner, contact details, equipment or project scope changes. Incorrect information may require withdrawal and a new application. If the project cannot be completed before expiry, the installer must withdraw the live voucher before making a new application. If the voucher has already expired, a new application is still needed but the expired application does not need to be withdrawn. You must give consent again, and the new application is assessed under the rules and values in force when it becomes properly made.

The role of installers

The installer is central to BUS. They assess the proposal, submit the voucher application, install and commission the system, provide evidence and redeem the voucher. This does not remove your need to compare contracts and ask questions: the installer is also the business selling and delivering the work.

What the installer is responsible for

• checking the property and proposed technology against BUS requirements

• holding the correct MCS certification for the technology

• providing accurate application and redemption information to Ofgem

• showing the grant as an upfront deduction in the quote and invoice

• designing and installing in line with relevant MCS standards

• meeting voucher deadlines and responding to evidence or audit requests

• providing commissioning, certification, warranty and handover documents

• requesting a statutory review where an eligible decision is challenged

What MCS certification means

MCS is a certification scheme for small-scale renewable installation companies and products. It sets technical standards, certifies installers and products, and supports the issue of MCS certificates. BUS requires the installer to be MCS certified for the relevant technology.

Certification is an important scheme condition, but it is not a guarantee that every installation will perform as expected or that every dispute will be resolved automatically. Check the live register, the legal name on the contract and which company is responsible if subcontractors are used.

Consumer codes and complaint routes

Installers working with consumers must meet the current approved consumer-code requirements. The relevant code may provide rules on quotations, deposits, contracts, dispute handling and consumer protection. Ask the installer which code applies and check membership directly.

Start an installation complaint with the installer in writing. If it is not resolved, use the applicable consumer code or MCS route for the type of issue. Ofgem deals with scheme administration, applications, consent, audit and compliance; it does not take over every contractual or workmanship dispute.

Other qualifications and permissions

BUS and MCS do not replace other legal or technical requirements. Gas work must be handled by a suitably registered Gas Safe engineer. Electrical work may need an appropriately qualified or registered electrician. Ground-source, water-source, biomass and listed-building projects may need planning, environmental, building-control, landlord, freeholder or land-right checks.

Ask the lead installer to identify which approvals are included, who applies, who pays and what happens if consent is refused. Do not accept a blanket statement that permission is never needed: England and Wales have different permitted-development rules, and local restrictions can apply.

Documents worth asking for

• an itemised quote with the BUS deduction clearly shown

• the heat-loss calculation and main design assumptions for a heat pump

• model numbers, product eligibility and proposed output

• emitter, cylinder, pipework and electrical schedules where relevant

• planning, noise, building-control or environmental evidence where needed

• payment stages, deposit protection and cancellation information

• warranty, servicing, call-out and complaint arrangements

• commissioning records, MCS certificate and final invoice after completion

If you disagree with a scheme decision

Only the installer can request a statutory review of specified Ofgem decisions. Current property-owner guidance says the request must be made within 28 days of the notice being reviewed. Ask for the decision and the installer response in writing so you understand the reason, evidence and deadline.

A review is different from a complaint about workmanship or the contract. Use the route that matches the issue, and keep records of dates, documents and conversations.

Costs and budgeting considerations

BUS reduces an eligible project by a fixed amount; it does not set the market price. Installation cost varies with the technology, building, heat demand, access, equipment, ground conditions, distribution system and work needed around the installation.

What published figures can - and cannot - tell you

Energy Saving Trust currently gives a typical air-source heat-pump installation cost of around £12,000. That is a broad consumer benchmark, not a quote for your home. A straightforward project may differ materially from one needing extensive radiator, cylinder, electrical or building work.

Ground-source systems are usually more expensive because of trenches or boreholes. Biomass cost depends on the boiler, store, fuel-feed equipment, flue and building work. Air-to-air systems can have lower equipment and wet-system costs, but the number of indoor units, electrical work and separate hot-water solution affect the total.

The cost areas most often missed

A practical budgeting method

1. Start with the gross quote before BUS so you can see the real project price.

2. Separate fixed items from provisional sums and work priced after opening up.

3. Check that all required radiators, cylinders, electrics and groundworks are listed.

4. Confirm who pays for permissions, surveys, scaffolding, access and making good.

5. Record the BUS value and the amount you must pay after the deduction.

6. Keep a contingency for genuine unknowns rather than relying on an unexplained percentage.

7. Compare servicing, warranty and likely replacement items over the ownership period.

How to compare quotes fairly

Ask installers to price the same scope where possible. Compare the design temperature, assumed heat loss, emitter changes, cylinder, controls, electrical work, equipment model, warranty, noise assessment, commissioning, aftercare and exclusions. A post-grant total is not comparable if one quote leaves major items outside the contract.

Be cautious with savings or payback figures that do not show energy-price assumptions, current fuel use, seasonal performance and the cost of all enabling work. Treat any illustration as a scenario, not a promise.

Finance and cashflow

Check deposit size, payment dates and what happens if the voucher is delayed, rejected or expires. Do not pay the grant-funded amount where the installer is required to deduct it upfront. If finance is used, confirm that legal ownership of the equipment passes to you and review the interest, fees, total repayable, security and early-settlement terms.

Clearwise does not provide regulated financial advice. Consider independent financial guidance where borrowing would affect your wider finances, and never let a grant deadline pressure you into credit you do not understand.

Running costs

A grant changes the upfront price, not the energy tariff or the amount of heat your building needs. Running cost depends on two separate questions: how much energy the system uses, and what you pay for that energy.

How heat-pump efficiency affects cost

Heat-pump performance is commonly described with COP for a particular test point and SCOP or seasonal performance for a longer period. These figures are ratios of heat delivered to electricity used. They do not, by themselves, show the bill because tariffs, standing charges, weather and household demand still matter.

Lower flow temperatures, well-sized emitters, good controls and lower building heat loss usually support better seasonal performance. High flow temperatures, frequent use of direct-electric backup, poor controls or a system working outside its intended conditions can increase electricity use.

Why a heat pump may cost more or less than your current system

Electricity normally costs more per unit than gas, while a heat pump uses fewer units of electricity than the units of heat it delivers. The balance between those two facts determines the result. Replacing direct electric heating, an older oil system or LPG can produce a different outcome from replacing an efficient mains-gas boiler.

Energy Saving Trust notes that air-source heat-pump savings vary with radiator sizing, tariff, controls and the system being replaced. Do not assume the same result as a neighbour, case study or national calculator. Ask for a property-specific annual energy estimate and the assumptions behind it.

Air-to-air and hot-water costs

An air-to-air heat pump normally provides space heating but not domestic hot water. Your total running-cost comparison therefore needs to include the separate hot-water system. Cooling can add summer electricity use if you choose to use it.

Biomass fuel and servicing costs

Biomass running cost depends on fuel type, local supply, delivery quantity, storage, boiler efficiency and servicing. Fuel prices can move independently of gas and electricity. Include chimney or flue work, ash handling, cleaning and maintenance rather than comparing only the advertised pellet price.

A running-cost checklist

What about future energy prices?

No installer can guarantee future electricity, gas, oil, LPG or biomass prices. Time-of-use tariffs may help some households shift heat-pump use, but access, meter requirements and savings depend on provider terms and how much demand can be moved without reducing comfort.

Use several price scenarios if the decision is sensitive to small changes. Recheck tariffs near installation and avoid describing a single forecast as the likely long-term outcome.

Benefits and key considerations

BUS can make a lower-carbon heating project easier to fund, but the technology still needs to fit the property and the people using it. The most useful comparison is balanced: what the system may improve, what changes it requires and which uncertainties remain.

Potential benefits

• a fixed upfront grant reduces the cost of an eligible installation

• heat pumps can reduce direct use of gas, oil or LPG at the property

• well-designed systems can provide steady, controlled space heating

• air-to-air systems can offer heating and, where used, cooling

• ground-source systems use a comparatively stable heat source

• off-gas homes may avoid oil or LPG storage and deliveries

• modern controls can make schedules and temperatures easier to manage

Operational carbon emissions can be lower than fossil-fuel heating, particularly as electricity generation becomes less carbon intensive. The actual reduction depends on the system being replaced, seasonal performance, electricity mix, fuel source and how the property is heated. BUS support is not proof of a specific carbon saving.

Practical limitations

• upfront cost can remain high after the grant

• radiator, pipework, cylinder or electrical changes may be needed

• outdoor and indoor equipment takes space

• noise, appearance and neighbour impact affect siting

• planning or other permissions can apply

• heating behaviour may differ from a high-temperature boiler

• running-cost savings are not guaranteed

• voucher timing can constrain the installation programme

Comfort and controls

Heat pumps often deliver heat for longer at lower temperatures than a boiler. Some people find this steady approach comfortable, while others need time to adjust schedules and controls. Comfort depends on room heat loss, emitter output, control settings and commissioning; it should not be promised from the technology name alone.

Ask the installer how the design maintains the chosen room temperatures in the local design conditions, how hot water is produced and what happens during defrost or very cold weather. Handover should explain the heating curve, thermostats, schedules and any backup settings.

Space, noise and permissions

Air-source units need airflow and careful positioning. Indoor cylinders, buffers, pumps or air handlers can affect cupboards and living space. Ground-source systems need suitable land, access or boreholes. Biomass needs a boiler room, flue and dry fuel storage.

Many domestic heat-pump installations can fall within permitted-development rights, but conditions differ between England and Wales and can change. Listed buildings, conservation areas, flats, leasehold homes, non-domestic buildings and local restrictions need particular care. Check with the relevant local authority and do not rely on a generic claim that permission is unnecessary.

Biomass-specific trade-offs

Biomass can be useful in a limited group of rural, off-gas properties, particularly where heat demand is high and fuel logistics are manageable. It is a combustion system, so particulate emissions, approved fuel, storage, deliveries, cleaning and local air-quality rules are central to the decision.

Questions to ask before committing

• What evidence shows the property and existing heating meet BUS rules?

• What heat demand and design conditions were used?

• Which work is included, excluded or provisional?

• What annual energy use is estimated and what assumptions support it?

• Which permissions, registrations and consumer-code protections apply?

• What happens if the voucher, permission or funding is not obtained?

• Who is responsible for commissioning, aftercare and complaints?

• Which alternatives were considered and why was this design proposed?

Combining with other grants

BUS can sometimes sit alongside support for other improvements, but public money cannot normally fund the same low-carbon heating installation twice. The safe approach is to identify each measure, each funding source and the interaction rules before work starts.

What can often be combined

Separate help for insulation, draught proofing, ventilation, solar PV or other distinct measures may be compatible with BUS where the other scheme allows it. A local-authority or supplier programme may also fund enabling work. Compatibility depends on the precise measure and funding agreement, not simply on the schemes having different names.

Give the installer copies of grant offers and completion documents. They need to confirm that no other public funding has been used for the BUS-funded plant. If a whole-house programme includes a heat pump, ask the programme administrator whether BUS is already built into the funding.

What usually cannot be combined

• two public grants paying for the same heat pump or biomass boiler

• BUS where the same low-carbon system was already publicly funded

• a second BUS grant for the same completed installation

• funding arrangements that prevent the owner owning the equipment

Different support across the UK

BUS applies only in England and Wales. Scotland and Northern Ireland have separate energy-advice and funding arrangements, and eligibility, amounts, providers and application steps can differ. Do not use BUS rules as a UK-wide template.

How the 2026 changes affect combinations

Air-to-air heat pumps now have a live BUS category for residential properties. Heat batteries do not have a separate BUS grant, although thermal storage can be a permitted supplementary appliance in some heat-pump configurations. Solar PV may work alongside a heat pump, but BUS does not pay for the PV system.

The £9,000 off-gas uplift is temporary and applies only to qualifying air-to-water and ground-source applications properly made from 21 July 2026 to 31 March 2027. It should not be described as a permanent grant or assumed in a project that has not reached the application stage.

Conclusion

The Boiler Upgrade Scheme can reduce the upfront cost of an eligible low-carbon heating system in England and Wales. The key is to treat the grant as one part of the decision. Property eligibility, system design, permissions, total cost, running-cost assumptions, installer responsibility and voucher timing all matter.

The main points to remember are:

• the installer applies, but the property owner gives consent directly to Ofgem

• current grants are £7,500, £2,500 or £5,000, with a limited £9,000 uplift

• a valid EPC is no longer mandatory for current applications, but evidence is still needed

• air-to-air heat pumps are supported only in residential properties

• fossil-fuel hybrids are not eligible and the old fossil system must be replaced

• the grant is an upfront discount and may leave substantial costs to pay

• vouchers have strict three- or six-month validity periods

• MCS certification is required but does not guarantee performance or workmanship

• running cost and carbon outcomes depend on the property and system in use

A well-supported decision starts with a clear assessment and comparable written quotes. It should end with a design, contract and funding position you understand, not only a headline grant figure.

What happens next

Start by recording your ownership, existing heating, EPC or alternative evidence, property constraints and likely budget. Check the current Ofgem and GOV.UK pages, confirm the installer on the MCS register and compare more than one itemised quote where practical.

Rules, evidence requirements, grant values, annual budgets, technical standards, energy prices and installer availability can change. This guide does not determine your property’s eligibility, design, permissions, performance or financial outcome. A property-specific assessment and a complete Ofgem application are needed.

Clearwise can make an introduction only with your consent. Any installer or other provider remains independent and decides whether it can assess or assist; an introduction does not guarantee acceptance, suitability, funding, availability or any particular result. You can also use the FAQs, glossary, useful organisations and references below before deciding what to do next.

Frequently Asked Questions

Eligibility and property questions

Grant values and technology choices

Application and process

Installation and compliance

Running costs and financial impact

Landlords, tenants and shared properties

Biomass and rural heating

Expanded BUS and future changes

Troubleshooting and consumer protection

Useful Organisations

Ofgem

Ofgem administers the Boiler Upgrade Scheme in England and Wales. Its current property-owner guidance explains eligibility, consent, applications, audits, reviews and complaint routes. Ofgem can answer scheme-administration questions but cannot pre-approve a property before a complete installer application.

• 0330 053 2006
• www.ofgem.gov.uk

GOV.UK

GOV.UK publishes the official consumer route for BUS and the Department for Energy Security and Net Zero notices setting approved grant categories, values and standards. Use it to check the current scheme position before relying on an amount or deadline.

• www.gov.uk

Energy Saving Trust

Energy Saving Trust provides independent consumer information on heat pumps, biomass, insulation, running-cost factors and funding across the UK. It does not decide BUS eligibility or issue vouchers.

• energysavingtrust.org.uk

Microgeneration Certification Scheme (MCS)

MCS certifies eligible small-scale renewable installers and products and provides a public installer search. BUS installers must hold the relevant certification. Check the live register and remember that certification is not a guarantee of savings, workmanship or grant approval.

• 0333 103 8130
• mcscertified.com

References

Still have questions?

If you’ve read this guide and you’re still unsure—about eligibility, suitable technologies, what a fair quote looks like, or how to avoid running cost surprises—that’s completely normal. Low-carbon heating is a big decision, and the “right” answer depends on the details of your property and priorities.

Speaking with an expert can help you:

• sense-check whether you’re likely to qualify for BUS before you invest time and money

• understand what upgrades (radiators, cylinder space, electrics, insulation) are truly necessary

• compare quotes on the things that matter (design quality, scope clarity, commissioning, aftercare)

• make a confident plan for budgeting and long-term running costs

If you’d like personalised guidance for your situation, consider arranging a conversation with an expert—your first consultation is free.