What would you do if your heating failed tomorrow: spend about £3,000 on a replacement gas boiler, or commit to a heat pump that could cost several times as much before any grant is applied?
That is the decision facing many UK homeowners as older boilers reach the end of their working lives. The figures look stark at first glance. A new gas boiler is familiar, relatively quick to fit and usually cheaper. An air-source heat pump involves more equipment, more preparation and a larger initial bill. Yet the gap narrows sharply once government support enters the calculation.
Picture a typical semi-detached house with a cold utility room, radiators on every wall and a boiler that has started making noises at inconvenient hours. The owner may think this is a simple like-for-like replacement. A heat pump turns the job into a wider examination of the home: insulation, heat loss, radiators, pipework and the space available outside. The price comparison is not just between two appliances. It is between two different installation projects.
The first quote: roughly £3,000 for a new gas boiler
In the UK, installing a new gas boiler in 2026 costs about £3,000 on average. That figure suits the straightforward replacement many households have in mind: the old boiler comes out, the new one goes in, and the existing heating system remains largely intact.
Gas boilers benefit from a mature installation network. Engineers are accustomed to working with them, spare parts are widely available and many homes already have the necessary gas connection, flue arrangement and hot-water setup. A replacement can often be planned around the existing layout rather than designed from scratch.
That does not mean every boiler installation will land at exactly £3,000. The price can rise if the boiler has to move, the flue needs changing, pipework requires attention or the property needs additional work to meet current requirements. The condition of the system matters too. A tired central-heating system may reveal its weaknesses as soon as a new boiler is fitted.
Still, the appeal is easy to understand. The cost is familiar, the process is comparatively contained and the new appliance can usually deliver heat in much the same way as the old one. For a homeowner choosing under pressure, that simplicity carries real weight.
Why an air-source heat pump starts much higher
A complete air-source heat pump installation typically costs between £8,000 and £18,000. The median installation price in 2024/25 was about £12,500, which gives a more realistic sense of where a standard project may sit inside that broad range.
The equipment itself is only part of the story. An air-source system extracts heat from outside air and delivers it into the home at lower flow temperatures than a conventional boiler. That can require larger radiators, changes to pipework or improvements to insulation, depending on the property. The installer must also assess where the outdoor unit can sit, how the system will connect to the hot-water cylinder and whether the home can retain heat efficiently enough.
Older British houses are often the difficult cases. A draughty terrace with undersized radiators may need more preparation than a recently renovated home with good insulation and generous emitters. Two properties with the same floor area can therefore receive very different quotes.
The outdoor unit is another practical detail that tends to appear late in the conversation. It needs suitable space, airflow and a position that works with the building and its surroundings. The indoor equipment may take up more room than the boiler it replaces, particularly if the property needs a hot-water cylinder. That can mean sacrificing cupboard space, rearranging a utility room or finding a new location altogether.
This is why a heat-pump quote should be read as a plan for the house, not simply a price for a machine. A suspiciously low figure may exclude work that becomes necessary later. A higher quote may include changes that make the system perform properly, although homeowners should still ask exactly what is covered.
The £7,500 grant changes the arithmetic
The standard Boiler Upgrade Scheme grant is £7,500 for an eligible heat pump replacing fossil-fuel heating. Applied to the typical installation range of £8,000 to £18,000, that leaves a homeowner paying approximately £500 to £10,500.
Against a new gas boiler costing around £3,000, the comparison becomes less predictable than the headline prices suggest. At the low end, a heat pump could cost only a few hundred pounds after the grant. At the high end, the remaining bill could still be more than three times the cost of the boiler.
The median example is clearer. A £12,500 heat-pump installation with a £7,500 grant would leave about £5,000 to pay, before any additional work outside the agreed installation scope. That is still more than the average gas-boiler replacement, but not the dramatic £9,500 difference implied by comparing £12,500 with £3,000 before support.
Eligibility matters. The grant is not an automatic discount available for every heating replacement, and the property and proposed system must meet the scheme’s conditions. The installer normally handles the application process, but the homeowner should confirm that the grant has been included in the written quotation rather than treating it as an assumption.
For eligible properties that are not connected to the gas network, a grant of up to £9,000 is available from 21 July 2026 to 31 March 2027. That makes the calculation more favourable for some off-grid homes, where a gas boiler may already involve a more complicated fuel arrangement. The timing is significant: anyone planning work in that window should check the rules and the installer’s ability to process the relevant support before signing a contract.
The hidden cost is often the house itself
A boiler replacement usually asks less of the building. A heat pump exposes its weak points.
If insulation is poor, rooms may lose heat faster than the system can comfortably replace it. If radiators are too small, they may need upgrading. If the existing cylinder is missing or unsuitable, a new hot-water arrangement may be required. None of these details automatically makes a heat pump the wrong choice, but each can move the final price away from the first estimate.
A proper heat-loss assessment is therefore more useful than a quick appliance quote. It should show how much heat each room needs and whether the proposed radiators and system design can meet that demand. Homeowners should be wary of a contractor who recommends a model based only on the size of the property. Floor area alone says little about insulation, glazing, room height or exposure to wind.
There can be smaller practical costs as well: electrical work, alterations to pipework, a base for the outdoor unit, condensate drainage or making good walls and floors after changes. Some projects need none of these. Others collect them one by one, like receipts left on a kitchen counter.
Gas installations have their own possible extras. A new boiler may need a revised flue, upgraded controls, system cleaning or changes to the condensate pipe. If the old boiler is being relocated, the labour and materials can climb quickly. The difference is that these additions are often familiar to installers and less likely to involve a wholesale rethink of the heating system.
Which installation cost makes sense for your property?
The cheapest upfront option is usually a gas boiler, particularly where the existing system is in reasonable condition and the replacement can stay in the same position. That choice may appeal to a homeowner who needs reliable heat quickly and cannot absorb a larger project.
A heat pump deserves closer attention if the boiler is due for replacement anyway, the home is reasonably well insulated or the property is outside the gas network. The grant can reduce the initial gap, and the project may be easier to justify when other renovation work is already planned. Replacing radiators during a wider refurbishment is less disruptive than doing it as an emergency measure in the middle of winter.
The quotation should separate the heat pump, cylinder, controls, labour, electrical work, radiator changes and any insulation recommendations. It should state the grant value and the amount left for the homeowner to pay. Ask whether removal of the old system, commissioning and follow-up adjustments are included. Those questions sound mundane, but they are where an apparently cheap installation can become expensive.
The final decision often comes down to more than the two headline figures. A boiler may fit neatly into the space left by its predecessor. A heat pump may ask for a larger redesign but receive enough grant support to make that redesign financially possible. Standing in the utility room with a tape measure, a damp patch by the old cylinder and three competing quotations, the homeowner is not really choosing between £3,000 and £12,500. They are choosing how much of the house, and how much of the future heating system, they are prepared to change.