Heat pump vs gas boiler: costs, comfort and practical changes

A heat pump and a gas boiler can both keep a properly designed home comfortable. The main differences are how they produce heat, the installation work, hot-water arrangements, controls and the prices you pay for energy.

A heat pump uses electricity to move heat rather than producing all its heat by burning gas. That gives it an efficiency advantage, but it does not automatically guarantee a lower bill. Your decision needs to compare complete systems supplying the same rooms and hot-water needs.

Checked 29 October 2026. The cost comparisons below are illustrative calculations, not quotations, product tests or forecasts of energy prices.

Heat pump versus gas boiler: the practical comparison

Question	Air-to-water heat pump	Gas boiler
Energy source	Electricity, with heat collected from outside air	Gas burned to heat water
Room heating	Water emitters designed for the proposed temperatures	Water emitters designed for the proposed temperatures
Hot water	Commonly a cylinder or another specifically designed storage arrangement	Combi or stored-hot-water options, depending on the system
Outside equipment	Outdoor unit requiring suitable location and airflow	Flue and gas-supply requirements
Existing radiators	Assessment determines which can stay	Assessment still matters, particularly after alterations
Controls	Often weather compensation and longer operating periods	Controls vary; compatible lower-temperature operation can also help condensing boilers
Energy bill	Heat demand, seasonal efficiency and electricity prices	Heat demand, seasonal efficiency and gas prices
Best starting point	Full survey and complete net quote	Complete replacement or repair quote for the real alternative

This comparison focuses on air-to-water heat pumps because they are the usual alternative to a radiator-based boiler system. Air-to-air heat pumps deliver heat differently and normally need separate domestic hot water.

Which is cheaper to install?

A straightforward boiler replacement and a conversion to a heat pump are different jobs. The conversion may include a cylinder, some radiator changes, electrical work and new pipe routes. Compare surveyed total prices, including those changes, rather than the retail price of the heat source alone.

The Energy Saving Trust's current air-source installation benchmark is around £12,000. Grant eligibility can materially change the customer contribution; a particular household may pay less or more than a headline example. See the published benchmark and our installation cost guide.

Obtain a genuine quote for the boiler alternative too. If you are replacing a failed boiler, that spending is relevant now. If the boiler is working well, treating an invented replacement cost as an immediate avoided expense can exaggerate the financial case for changing it.

How grants change the comparison

In England and Wales, the Boiler Upgrade Scheme can support eligible replacement installations. Funding varies by technology and circumstances; do not deduct a grant twice from a supplier's advertised post-grant price. Scotland has separate arrangements and the scheme does not cover Northern Ireland.

Ask who applies, when eligibility is confirmed and what happens if funding is refused. Use the confirmed contribution in your comparison. Check the official grant rules.

Which is cheaper to run?

Use the same useful heat requirement. For a boiler, purchased gas must cover conversion losses. For a heat pump, purchased electricity depends on seasonal system performance.

Assume 12,000kWh of useful annual heat, gas at 6p/kWh, electricity at 25p/kWh and a boiler at 90% seasonal efficiency. These inputs demonstrate the calculation and are not current tariff quotations.

System assumption	Purchased energy	Annual heating energy cost
Gas boiler at 90%	About 13,333kWh gas	About £800
Heat pump at seasonal efficiency 2.5	4,800kWh electricity	£1,200
Heat pump at seasonal efficiency 3.0	4,000kWh electricity	£1,000
Heat pump at seasonal efficiency 3.5	About 3,429kWh electricity	About £857
Heat pump at seasonal efficiency 4.0	3,000kWh electricity	£750

The heat pump uses fewer purchased units in every row but only the final example has a lower energy cost than this boiler. This is why a statement such as “three times as efficient” does not establish a bill saving.

At electricity costing 20p/kWh, the efficiency-3.5 example falls to about £686. Unit prices and the performance actually achieved change the answer substantially. Add standing charges, servicing and other cost differences separately.

The break-even efficiency

Multiply the electricity unit price by boiler efficiency, then divide by the gas unit price. With 25p electricity, 90% boiler efficiency and 6p gas, the heat pump needs seasonal efficiency 3.75 to match the boiler's energy cost.

That is an energy-only threshold. It does not include capital spending, avoided gas standing charges, finance or repairs. Use the same performance boundary for all the heat pump's relevant electrical inputs. Read about measured heat-pump performance.

What does the comparison look like over ten years?

Separate initial spending from recurring costs and show the assumptions. A simple ownership table can reveal where an apparent advantage comes from.

Illustrative ten-year input	Heat pump	Boiler alternative
Customer installation cost	£4,500	£3,000
Annual heating energy	£750	£800
Annual service assumption	£150	£100
Ten years of the above, unchanged	£13,500	£12,000

These invented installation and service inputs are not market averages. The table excludes finance, repairs, replacement, inflation and standing charges. On these particular assumptions, lower heat-pump energy spending is offset by a higher assumed service cost, leaving the initial cost difference unrecovered.

Change the inputs to your quotes and expected performance. If removing gas genuinely avoids a standing charge, add that saving. If you keep gas for cooking, include the continuing charge instead. A sensitivity check with less favourable efficiency and prices is more useful than one optimistic total.

Will a heat pump keep the house as warm?

The system should be designed to reach agreed room temperatures in the relevant cold-weather conditions. Heat-pump suitability is not decided solely by the age of the building or how hot the radiator feels.

Ask for a room-by-room heat-loss assessment and emitter schedule. A room needing more heat than its radiator can provide at the proposed water temperature needs a design response: a different emitter, reduced heat loss or another justified change.

Energy Systems Catapult's demonstration project found successful installations across the housing types tested. That supports investigating older and varied homes, while leaving the individual survey essential. Read the project evidence.

Do radiators and pipes need replacing?

Not automatically. Existing radiators may be suitable, or selected rooms may need larger or different emitters. Ask for the calculated output at the actual proposed flow, return and room temperatures.

Narrow pipes also need assessment rather than a blanket verdict. The designer should consider required flow, pressure loss and routing. A short narrow section can present a different problem from an entire distribution system. Energy Saving Trust's microbore guidance explains why the answer is design-specific.

Avoid removing necessary upgrades just to make the installation quote match a boiler price. Equally, ask for the reason if every radiator is to be replaced without a room-by-room explanation.

What changes if you have a combi boiler?

A combi normally supplies domestic hot water on demand. A conventional air-to-water heat-pump installation commonly uses storage, so find out where it will go and what usable supply and recovery it offers.

Describe your household's actual use: consecutive showers, baths, guests and peak times. Ask whether the proposed arrangement covers that use without relying on unexpected amounts of direct electric backup.

Compare the full installed hot-water service, including any cupboard alterations, electrical work and maintenance. Alternatives to a conventional cylinder exist, but require their own compatibility, capacity and cost checks. See our hot-water guide.

Illustrative image. The equipment and layout for a particular home must be assessed as part of its design.

Controls, schedules and daily use

Heat pumps are often designed around longer operation with lower heating-water temperatures. That does not mean forcing the compressor to run continuously, nor does it mean every home should copy the same schedule.

Ask the installer to demonstrate ordinary controls and explain weather compensation, hot-water timing, holiday mode and any backup heating. Keep a record of the commissioned settings before making changes.

If you work away from home, discuss the occupancy pattern before installation. If you use a time-of-use tariff, compare the cost of the whole household and preserve comfort rather than chasing the cheapest hours at any cost. The controls toolkit explains the underlying principles.

Noise, maintenance and reliability

Gas boilers and heat pumps create different sounds and have different siting requirements. A heat pump's outdoor fan and compressor need a location assessed for airflow, neighbouring windows, vibration, access and the applicable rules. Do not treat a brochure's lowest sound figure as a complete assessment.

Ask for service prices, warranty conditions and the local repair route for each option. Remote monitoring can help diagnosis but does not replace a commitment about who attends a fault. Neither technology comes with a universal promise of a fixed lifespan or maintenance-free operation.

Choose the installer as carefully as the equipment. Government guidance on finding an installer recommends asking about design, disruption, supply changes and aftercare.

When is each option worth considering?

A heat pump deserves a detailed quote if the house can accommodate the complete design, the contribution is affordable and its practical or environmental benefits matter to you. A failing heating system or planned renovation can make the timing more convenient.

Keeping a working boiler while preparing the house may be sensible if immediate replacement has a weak financial case or an unresolved practical obstacle. Ask what improvements remain useful regardless of the eventual heat source.

The choice should follow your actual circumstances. Our “Are heat pumps worth it?” guide provides a wider decision framework.

Heat pump versus boiler FAQs

Is a heat pump always cheaper than gas?

No. Seasonal efficiency, unit prices and the boiler being replaced determine the heating energy comparison. Whole-house costs add installation, charges and aftercare.

Do I need underfloor heating?

No universal requirement applies. Suitable radiators and other emitters can be part of a properly designed system. Their output must match the relevant rooms at the proposed temperatures.

Can I keep both systems?

Hybrid arrangements exist, but bring different controls, costs and funding rules. Do not assume that retaining a fossil-fuel boiler qualifies for the same support as a complete replacement.

Does higher maximum water temperature mean a better heat pump?

Not by itself. Compare output and efficiency at your design conditions, along with emitters, hot water and controls. A capability quoted for particular conditions is not a recommendation to run at maximum temperature.

Should I compare monthly payments?

Compare annual energy use and total costs first. Direct Debits can reflect account credit or debt, and finance payments may conceal interest or different contract lengths.

Related guides for your next step

To turn heat demand, efficiency and electricity prices into a budget, use the heat pump running-cost calculator.

For supplier time windows and whole-house billing, see our heat pump tariff comparison.

If the proposal does not suit the property or budget, compare alternatives to heat pumps using the same household needs.

Sources and method

The sources linked above provide technical, installation and feasibility context. All financial examples are our own calculations with deliberately explicit assumptions. We have not tested either system or predicted a particular home's savings.

Images are AI-generated editorial illustrations.