On average, swapping an old gas boiler for an air source heat pump costs between £4,000 and £15,000 once you factor in the equipment, installation and any extra work needed on your radiators or hot water cylinder.
The good news is that government grants, ongoing running cost savings and the rising price of gas mean the real cost is often much lower than people expect, and this guide breaks down every part of that cost so you can plan with confidence.
How Much Does It Cost To Replace A Gas Boiler With A Heat Pump?
The cost to replace a gas boiler with a heat pump typically ranges from £4,000 to £15,000 for an air source heat pump once the £7,500 government grant has been applied, with most Kent homes falling somewhere in the £6,000 to £11,000 bracket after the grant is deducted.
This price covers the heat pump unit itself, the hot water cylinder, labour, and any pipework changes needed to get your home ready for a lower temperature heating system. Ground source heat pumps sit at the higher end of the market, often costing between £11,500 and £27,500, because they require digging boreholes or trenches in the garden, which adds significant groundwork costs.
Most homeowners in Kent choose an air source system because it is cheaper to fit, needs no digging, and suits the typical semi-detached and terraced housing stock found across the county. The final figure always depends on the size of your home, how much insulation you already have, and whether your existing radiators are up to the job.
What Factors Affect The Cost Of Replacing A Boiler With A Heat Pump?
The factors that affect the cost of replacing a boiler with a heat pump include:
- the size of your property
- the type of heat pump you choose
- the condition of your existing radiators and pipework
- the amount of insulation in your home
- and whether you qualify for a government grant
A larger four or five bedroom detached house will usually need a bigger heat pump with a higher heat output, which naturally pushes the price up compared with a smaller flat or terraced house. Homes with older, undersized radiators often need some or all of them replaced with larger units, since heat pumps work most efficiently at lower water temperatures and need bigger surface areas to release the same amount of heat into a room.
The type of hot water cylinder you need also matters, as heat pump systems require an unvented cylinder if you do not already have one fitted. Access to your property plays a role too, because if the outdoor unit needs to be positioned somewhere awkward, or if scaffolding is required, this can add to labour costs.
Finally, the level of insulation in your loft, walls and floors affects how much heat your home loses, which in turn determines the size and cost of the heat pump needed to keep you warm.
Property Size And Heat Loss
The bigger and less insulated your home, the more heating capacity it needs, and this is worked out through a heat loss calculation that every reputable installer, including Guscott Heating, will carry out before quoting you a firm price.
A well insulated two bedroom terrace in Kent might only need a 5kW heat pump, while a large draughty farmhouse could require a 12kW or 16kW system, and the price difference between these can easily be a few thousand pounds.
Radiator And Pipework Upgrades
Roughly a third of homes need at least some radiators upgraded when moving from a gas boiler to a heat pump, since heat pumps run at lower flow temperatures, typically between 35°C and 55°C compared with 60°C to 80°C for a gas boiler.
If your radiators are already oversized or you have underfloor heating, you may not need any changes at all, which keeps costs down.
How Do Government Grants Reduce The Cost Of A Heat Pump?
Government grants reduce the cost of a heat pump through the Boiler Upgrade Scheme, which currently offers £7,500 off the cost and installation of an air source or ground source heat pump for most homes in England, including everywhere across Kent.
This grant is paid directly to your MCS certified installer and taken off your quote upfront, so you never have to claim the money back yourself or wait for a refund. From 21 July 2026, homeowners who are replacing an oil or LPG heating system, rather than mains gas, can claim an even higher grant of £9,000, reflecting the government’s push to move rural and off-grid properties away from fossil fuels faster.
There is no income test and no specific EPC rating requirement to qualify, which makes the scheme accessible to a wide range of households, from first time buyers to retired homeowners and landlords with rental properties.
On top of the grant, heat pump installations also benefit from a 0% rate of VAT, which is a saving worth having when you consider that VAT on many home improvements sits at 20%.
To be eligible, the property must have a valid Energy Performance Certificate with no outstanding recommendations for loft or cavity wall insulation, and the work must be carried out by an MCS certified installer such as Guscott Heating.
Who Can Apply For The Boiler Upgrade Scheme?
Homeowners, private landlords and even second home owners across Kent can apply for the Boiler Upgrade Scheme, provided the property is not new build, social housing, or already in receipt of other government funding for a heat pump.
Landlords should note that the grant does apply to rental properties, which makes now a sensible time to upgrade ageing gas boilers in tenanted homes before energy efficiency rules for rental properties tighten further in the coming years.
Is It Cheaper To Run A Heat Pump Than A Gas Boiler?
Running a heat pump is often similar in cost to running a gas boiler at today’s energy prices, and can be noticeably cheaper if your heat pump is well sized and your home is reasonably insulated.
Based on current Ofgem price cap rates, with electricity priced at around 24.5p per kWh and gas at around 6.4p per kWh, an efficient heat pump with a coefficient of performance, known as a COP, of 3.5 or higher delivers heat at roughly 7p per kWh, which is very close to the 7.1p per kWh cost of heat from a modern A rated gas boiler.
For a typical three bedroom semi-detached home in Kent using around 12,000 kWh of heat a year, this works out to annual running costs of roughly £840 for a heat pump against approximately £880 to £1,000 for a gas boiler, though the exact figures shift depending on how efficiently each system runs in your specific home.
Heat pumps that are poorly sized or badly installed, with a lower COP of around 2.5, can end up costing more to run than a gas boiler, which is why correct sizing and a proper heat loss survey are so important.
As gas prices rise faster than electricity over the coming years, and as heat pump technology continues to improve efficiency, the running cost gap is expected to widen further in favour of heat pumps.
Why Does Heat Pump Efficiency Vary So Much?
Heat pump efficiency varies because the coefficient of performance depends heavily on installation quality, home insulation and correct sizing, with a well installed system typically achieving a COP between 3.0 and 4.0, meaning it produces three to four units of heat for every one unit of electricity used.
A poorly installed or oversized heat pump can drop to a COP of 2.5 or lower, which significantly increases running costs, which is exactly why choosing an experienced MCS certified installer like Guscott Heating, rather than the cheapest quote available, makes a real difference to your long term bills.
How Long Does It Take To Install A Heat Pump?
Installing a heat pump typically takes between two and five days on site once the work begins, with a straightforward swap in an average three bedroom home usually completed within two to four days.
The full journey from your first enquiry through to a fully working system tends to span around six to twelve weeks, since this includes the initial home visit, a detailed heat loss survey, equipment ordering, grant paperwork, and scheduling the installation team.
On the first day, engineers usually fit the outdoor unit and run the necessary pipework, the second day often covers the hot water cylinder and internal controls, and a third day, if needed, is used for any radiator upgrades and final commissioning.
You will generally be without heating and hot water for one working day during the switch, and reputable installers plan this carefully to keep disruption to a minimum. Homes needing several new radiators, underfloor heating changes, or more complex electrical work may take closer to a week on site, though this is still far less disruptive than most homeowners expect.
What Financial Support Is Available Beyond The Boiler Upgrade Scheme?
Financial support beyond the Boiler Upgrade Scheme includes the ECO4 scheme for lower income households and some local authority grants under wider energy efficiency programmes, though the Boiler Upgrade Scheme remains the main source of funding for most homeowners.
ECO4 is aimed primarily at low income and vulnerable households and can, in some cases, cover a heat pump installation in full alongside other home improvements like insulation, though eligibility depends on specific benefits received and property circumstances.
Some councils in Kent also run local energy efficiency schemes from time to time, so it is worth checking with your local authority alongside speaking to your installer, since availability and criteria change throughout the year.
Landlords upgrading rental properties may also find the investment pays for itself faster given the upward pressure on minimum energy efficiency standards expected for privately rented homes in the coming years. Guscott Heating stays up to date with all current funding options and will always let you know what you might be eligible for as part of your free quote.
Switching From A Gas Boiler To A Heat Pump
Switching from a gas boiler to a heat pump is a significant investment, but between the £7,500 government grant, 0% VAT, and running costs that are now broadly comparable to or cheaper than gas in many Kent homes, the financial gap has closed considerably compared with just a few years ago.
Beyond the numbers, a heat pump also offers a quieter, cleaner and lower carbon way to heat your home, with no combustion, no flue, and none of the safety checks required for gas appliances.
As gas prices remain volatile and government policy continues to favour low carbon heating, more homeowners and landlords in Kent and across the wider South East are choosing to make the switch now rather than waiting until their existing boiler fails and they are forced into a rushed decision.
Ready To Switch? Get Your Free Heat Pump Quote From Guscott Heating
If you are ready to find out exactly what the cost to replace a gas boiler with a heat pump would be for your own home, Guscott Heating is here to help every step of the way. We provide air source heat pump installation across the whole of Kent, covering towns and areas including Maidstone, Canterbury, Ashford, Tunbridge Wells, Dartford, Sevenoaks, Medway, Tonbridge, Sittingbourne, Faversham, Herne Bay, Whitstable, Folkestone, Dover, Gravesend and the surrounding villages.
Get in touch today for a free heat pump quote tailored to your location and take the first step towards a warmer, cheaper to run and more sustainable home.
Our MCS certified team will carry out a thorough, no obligation survey of your property, talk you through every available grant and financing option, and provide a clear, honest quote with no hidden extras.
Frequently Asked Questions
Can I Keep My Radiators If I Switch To A Heat Pump?
Yes, many homes can keep their existing radiators if they are already reasonably sized, though roughly a third of properties benefit from upgrading one or more radiators to slightly larger units so the lower temperature heat from the pump still warms the room effectively. Your installer will assess each radiator individually during the heat loss survey rather than assuming a blanket replacement is needed.
Will A Heat Pump Work In A Very Cold Kent Winter?
Yes, modern air source heat pumps are designed to work effectively even when outdoor temperatures drop close to freezing, and many models continue operating efficiently down to minus fifteen degrees Celsius or lower, which comfortably covers typical winter conditions across Kent. Efficiency does dip slightly on the coldest days, but a correctly sized system will still keep your home warm throughout the year.
Do I Need Planning Permission To Install A Heat Pump In Kent?
Most homeowners in Kent do not need planning permission to install an air source heat pump, as these installations typically fall under permitted development rights, provided the outdoor unit meets standard size and noise limits and is positioned appropriately away from boundaries. Listed buildings and some conservation areas may require additional consent, so it is worth checking with your local council or asking your installer to confirm before work begins.
How Noisy Is A Heat Pump Compared To A Boiler?
A modern air source heat pump typically produces around 40 to 60 decibels of sound at close range, which is roughly comparable to a quiet conversation or a domestic fridge, and this noise is usually barely noticeable from a few metres away or inside the home. This is generally quieter than many people expect, and positioning the unit sensibly during installation helps minimise any impact on you or your neighbours further.
What Happens To My Old Gas Boiler When It Is Removed?
Your old gas boiler is safely disconnected, removed and responsibly recycled by your installer as part of the switch, with the gas supply to that appliance capped off by a Gas Safe registered engineer to ensure everything is left safe and compliant. Guscott Heating handles this removal as a standard part of every heat pump installation, so you do not need to arrange separate disposal yourself.
