Heat Pump vs Gas Boiler: A Comparison for UK Households

If your boiler is on its last legs, you have a decision to make that will shape your home's comfort and your bills for the next decade or more. A like-for-like gas boiler replacement is the familiar path. A heat pump is the one your installer, your neighbour and the government all seem to be talking about. Both can heat a UK home well. They differ in how they work, what they cost to buy and run, and how much disruption the switch involves.

Here is a grounded look at the practical differences, so you can weigh up what makes sense for your property rather than for a showroom brochure.

How the two systems actually work

A gas boiler burns fuel to heat water, which then travels to your radiators or underfloor heating. It runs hot and fast: typical flow temperatures sit around 70–80°C, which is why radiators can be small and still feel scorching.

A heat pump works differently. It moves heat from outside air (or the ground) into your home using electricity, a bit like a fridge running in reverse. Because it moves heat rather than creating it by burning something, it can produce several units of heat for every unit of electricity it uses. The trade-off is that it runs at lower temperatures, usually 35–55°C. That means it heats steadily rather than blasting, and it works best when your home holds warmth well.

Why flow temperature matters

Lower flow temperatures change what your radiators need to do. A heat pump often needs larger radiators, or the same radiators with more insulation behind them, to deliver the same comfort. This is the single biggest reason heat pump installations vary so much in price: some homes need almost no changes, others need most of the radiators swapped.

Upfront costs: what you actually pay

A straightforward gas boiler replacement is usually the cheaper purchase. A new combi boiler fitted by a registered engineer typically costs less than a full heat pump installation, sometimes by a wide margin. Heat pumps cost more because of the unit itself, the cylinder for hot water, and the labour involved in surveying, sizing and often upgrading radiators and pipework.

That gap narrows considerably once grants are applied, and it narrows further if you are already planning to replace radiators or renovate. The honest position is that no two quotes look alike. Get at least three, and ask each installer to break down the cost of the pump, the cylinder, any radiator changes and any electrical work.

Grants and financial support

The main support route in Great Britain is the Boiler Upgrade Scheme, which offers a grant towards the cost of installing a heat pump in England and Wales. Scotland has its own Home Energy Scotland grant and loan scheme, and Northern Ireland has separate arrangements. Grant amounts, eligibility and application processes change, so check the current rules on the official government pages before you rely on any figure you have read elsewhere.

Some installers will handle the grant application for you. If they do not, you may need to apply yourself before work starts. Do not assume a grant is automatic, and do not sign anything until you understand who is claiming what.

Running costs: the part nobody can promise

Running costs depend on three things: how much heat your home loses, how efficient the system is, and the price of gas versus electricity. Electricity costs more per unit than gas, but a heat pump delivers more heat per unit because of its efficiency. Whether that leaves you better or worse off depends heavily on your tariff and your home.

Things that tilt the balance towards a heat pump:

• Good insulation, draught-proofing and double or triple glazing
• A well-sized system with correctly sized radiators or underfloor heating
• A smart tariff that shifts some usage to cheaper overnight periods
• Solar panels, which can offset daytime electricity use
• Running the heating at a steady low temperature rather than in short bursts

Things that tilt it towards gas:

• A poorly insulated or very draughty property
• Small radiators that would be expensive to replace
• No space for a hot water cylinder
• Standard-rate electricity with no flexibility in when you use it

If you want a realistic figure, ask an installer for a heat loss survey and an estimated annual running cost based on your actual property, not a generic average. Anyone quoting a single national number is guessing.

Practical suitability for different UK homes

Heat pumps suit more homes than many people assume, but they suit some far more easily than others.

Well-insulated houses with gardens or driveways

These are the easiest conversions. A semi-detached or detached house with cavity wall insulation, decent loft insulation and space for an outdoor unit is close to ideal. Radiators may need upsizing, but the work is usually manageable.

Flats and homes without outdoor space

This is where heat pumps get tricky. An air source unit needs somewhere outside to sit, with enough clearance for airflow and ideally away from bedroom windows because of noise. Flats may need permission from a landlord or freeholder, and communal solutions are rare. High-temperature heat pumps exist and can reduce the need for radiator changes, but they cost more and are not a universal fix.

Period properties and off-gas-grid homes

Old stone cottages and listed buildings need careful assessment. Solid walls, single glazing and original features make heat loss harder to tackle. Off the gas grid, though, the maths changes: if you currently heat with oil, LPG or electric storage heaters, a heat pump is often a strong contender on both cost and convenience.

Disruption, noise and daily life

A gas boiler swap is often a day's work. A heat pump installation typically takes several days, sometimes longer if radiators and pipework are being changed. You will have an outdoor unit running, though modern models are quiet enough that most neighbours will not notice.

Day to day, the biggest adjustment is mindset. Heat pumps prefer to run for longer at lower temperatures. Setting a steady schedule rather than turning the heating off and on tends to give better results and lower bills.

How to decide

Start with a heat loss survey, not a sales pitch. Then compare like for like: get a gas boiler quote and a heat pump quote for the same property, both including any radiator and cylinder work. Check current grant eligibility yourself, and ask about tariffs that reward flexible electricity use.

If your home is reasonably insulated, you have outdoor space and you plan to stay put for years, a heat pump is worth serious consideration. If your property is hard to insulate, short on space, or you need the cheapest possible replacement this month, a modern gas boiler may still be the sensible choice while you plan improvements. Either way, an independent, well-reviewed installer will tell you more in an hour than any comparison table can.

For advice on grants, eligibility and installation standards in your area, speak to an accredited installer or your national energy advice service before committing to work.