Is my home small enough for a free heat pump?

If you have seen a heat pump described as free for smaller homes and flats, you may wonder what “small” means. The honest answer is that the scheme does not draw that line, and neither does ByEco with a number. This guide sets out what the rules do say, what does decide the outcome, and how to find out for your own home.

The short answer: we found no size limit, so what decides it?

In the rules we read, no fixed size makes a home “small enough”. A heat pump may be free of charge for an eligible home after the £7,500 Boiler Upgrade Scheme (BUS) grant, subject to survey and eligibility, and what is left to pay depends on three things: the size of the system the home needs, the rest of the installation, and what the survey finds.

For an eligible apartment the outcome can be a heat pump free of charge after the grant, subject to survey and eligibility, but that is not a promise for every apartment or every home, and it is not something to assume from a floor plan. Our guides to free heat pumps for flats and to whether you can get a free heat pump cover the wider picture.

What the scheme says about size

GOV.UK lists the standard grant as £7,500 towards an air source heat pump. Ofgem’s guidance for installers gives the same figure for an air-to-water heat pump, which GOV.UK says is sometimes what an air source heat pump is called. We searched GOV.UK’s Boiler Upgrade Scheme pages, Ofgem’s installer guidance and the Boiler Upgrade Scheme Regulations for floor area, square metres, bedrooms and property size, and found no mention of any of them as a condition of the grant.

The only size figures in the rules are about the heat pump, not the home:

• A maximum. GOV.UK and Ofgem set 45 kWth as the largest capacity for an individual heat pump system. That limit is on the equipment, not on the home.
• A match to the home. Ofgem says the heat pump system must have enough thermal capacity to provide all of the space heating needs of the property. So the system has to fit the home, which is why the calculation below matters.

In short, in the rules we read the standard grant does not change with the size of your home. What changes with the home is the heat pump it needs and the work to fit it.

What decides whether anything is left to pay

The standard grant is a fixed amount that your installer takes off the quote. Whether the remaining balance is anything at all depends on the home.

1. The system your home needs

The MCS design standard (MIS 3005-D) says a heat load calculation should be performed on the building to size and select the heat pump. That calculation looks at how much heat the building loses, rather than counting bedrooms. A smaller home with less heat loss often needs a smaller system than a large detached house, but that is a tendency and the calculation decides. Our guide to what size heat pump you need explains how it works.

2. The rest of the job

The heat pump itself is not the whole quote. The survey looks at whether radiators or pipework need changing, where the unit will go and how far pipes must run, any electrical work, and how hot water will be provided (ask any installer to spell that out). Some systems have no outdoor unit at all; see can you get a heat pump without an outdoor unit?

3. The survey itself

Two homes of similar size can come out differently, and a home that looks modest can surprise you. Insulation, windows, the age of the building and the existing heating all feed into the result, which is why ByEco gives a figure only after it has seen the property.

Why ByEco looks at smaller homes and apartments

ByEco’s view is that bigger houses mean more work, more material and more labour, while smaller houses and apartments need less material and less labour. So ByEco can offer a heat pump free of charge under the scheme to eligible smaller homes and apartments, subject to survey and eligibility.

That is ByEco’s own commercial explanation, not a rule of the scheme, and it does not mean the scheme sets a size. We deliberately do not define “smaller” with a number of bedrooms or square metres, because the survey is what settles it.

Apartments, terraces, semis, bungalows and detached houses

No type of home is ruled out by size. GOV.UK’s list of properties that cannot get a grant names most new builds, social housing and properties already given government funding for a heat pump or biomass boiler. It sets no floor area or bedroom condition. Here is what tends to matter for each, as general guidance rather than a rule:

Apartments are the case where ownership needs the most care. GOV.UK says most flats are leasehold and that you own a leasehold property for a fixed period of time. The scheme’s test is that you own the property, and the sources do not spell out how a leasehold flat is treated, so ask the installer how ownership will be shown before they apply. The Leasehold Advisory Service says you might need your landlord’s permission before altering your home even if you already have planning permission, and lists installing a heat pump on the external wall among the changes a lease might restrict.

A larger detached house is not excluded. It is more likely to need a bigger system and more work, so more may be left to pay, but that is a tendency and not a rule. Whether a particular house qualifies for a heat pump free of charge depends on its survey and its eligibility, as for any other home.

What the free survey (assessment) involves

ByEco’s free survey is how the questions above get answered for your home, and you may also hear it called the free assessment. At the visit, the surveyor:

• carries out the heat load calculation that sizes the heat pump (see our survey guide);
• checks your radiators and pipework, and where a unit could go;
• checks your existing heating against the eligibility rules, and how ownership will be shown; and
• confirms how hot water will be provided.

You then receive an itemised quote. Ofgem’s guidance says installers must show the total quote amount without the grant deducted and the total with it deducted, and must deduct the full grant value before you pay anything. If you are happy with the quote, ByEco can go ahead.

What happens if the quote is more than the grant

You pay the difference. GOV.UK describes the scheme as a grant “to cover part of the cost of replacing fossil fuel heating systems”, not a promise to meet the whole bill. The standard grant is a fixed £7,500 and the installer deducts it from the quote, so if the quote is higher you pay the balance, and what the balance is depends on the system, the work and the survey. Ofgem says installers must not request or accept payment of the grant amount from the property owner, so the grant itself is never something you pay for.

For what drives the rest of the quote, see our heat pump costs in Manchester page and the Boiler Upgrade Scheme guide. We do not quote a price in advance, because it depends on the home.

Eligibility in plain English

GOV.UK says you are eligible for a grant if both of these are true. You must:

• own the property you’re applying for (including if it’s a business, a second home, or a property you rent out to tenants); and
• be replacing fossil fuel heating systems, such as oil, gas, electric or LPG (liquefied petroleum gas).

Ofgem adds that the heat pump must fully replace the existing fossil fuel or electric heating system, except where supplementary heating appliances are permitted. Electric heating that does not include a heat pump counts as the old system, for example storage heaters or electric panel radiators.

You cannot get a grant for:

• most new build properties. A new build the developer is still building is not eligible, though GOV.UK says you may be able to get a grant if you move into a finished new build with a fossil fuel boiler;
• social housing (homes owned or managed by councils, housing associations or registered social landlords, or other organisations providing housing at below market rent or through shared ownership schemes for people in housing need). Ofgem says a former social home sold through Right to Buy and now privately owned may be eligible;
• a hybrid system, for example a gas boiler combined with an air source heat pump; or
• a property already given government funding or support for a heat pump or biomass boiler.

Ofgem also says cascade systems heating multiple unrelated properties, such as flats, are not eligible, so this guide is about a heat pump for your own home. These are the scheme’s rules, not ByEco’s, and the survey checks whether your home is eligible.

What to have ready for the assessment

Ofgem lists what a property owner confirms when an installer applies, and it is a useful checklist. Have these to hand:

• Your full name and the installation address.
• How you own the property, or that all co-owners agree. For a flat, have your lease to hand and note who the freeholder or managing agent is.
• What heats the home now: boiler, storage heaters, electric panels, oil or LPG.
• Whether the home has had other support from public funds or government schemes for heating, for example ECO.
• If you rent the home out, that you have told the tenant about the installation.
• Any floor plan, past surveys or notes on insulation and windows. These are optional, and they help the surveyor.

Your consent is needed before the installer’s application can go ahead, and Ofgem contacts you to confirm it. For an air source heat pump the voucher is valid for three months from the day it is issued, so sort out any freeholder permission first.

Where ByEco stands and what to do next

ByEco is MCS certified for air source heat pump installation (certificate IAA10330), and we apply for the £7,500 Boiler Upgrade Scheme grant on your behalf.

A 100% free-of-charge heat pump is possible for an eligible apartment under the Boiler Upgrade Scheme, subject to survey and eligibility. If your home may be eligible, get in touch for your free assessment (survey) so ByEco can start your Boiler Upgrade Scheme application while funding is available.

The scheme is funded in budgets and its rules and funding can change, so it is sensible to ask for your assessment early. Budget 2026 says the government will “maintain the Boiler Upgrade Scheme at current funding levels of £400 million in 2027-28”, and under the current Regulations no boiler upgrade voucher can be issued after 31 December 2029. Ofgem’s installer guidance also says it cannot issue new vouchers once the budget threshold has been met, that it may run a queue if the available budget runs out, and that it publishes monthly reports of the remaining annual budget. None of these sources says the grant is about to run out. For general information, see our heat pumps and grants pages.

Sources

Every figure on this page was checked against primary sources on 7 November 2026. Grant rules, planning rules and prices change — if you are reading this much later, verify before acting.

• GOV.UK — Apply for the Boiler Upgrade Scheme: what you can get
• GOV.UK — Apply for the Boiler Upgrade Scheme: check if you’re eligible
• GOV.UK — Apply for the Boiler Upgrade Scheme
• Ofgem — Boiler Upgrade Scheme: guidance for installers
• Ofgem — Boiler Upgrade Scheme guidance for installers V5.2 (PDF)
• legislation.gov.uk — Boiler Upgrade Scheme (England and Wales) Regulations 2022, regulation 5
• legislation.gov.uk — Boiler Upgrade Scheme (England and Wales) Regulations 2022, regulation 15
• MCS — MIS 3005-D Heat Pump Design Standard, Issue 3.0
• HM Treasury — Budget 2026
• GOV.UK — Leasehold property
• The Leasehold Advisory Service — Alterations and home improvements