The question of whether to choose an air source heat pump or a gas boiler is becoming increasingly relevant for UK homeowners. With the government's push toward net zero, the Boiler Upgrade Scheme offering grants for heat pump installations, and rising energy costs, many people are weighing up their options. The right choice depends on your property, your budget, and your priorities. This guide walks through the key factors to help you make an informed decision.
How Each System Works
A gas boiler burns natural gas to heat water, which is then circulated through your radiators and taps. It is a well-established technology that most UK homes have relied on for decades. A gas boiler heats water to high temperatures quickly, making it well suited to the standard radiators and pipework found in most properties.
An air source heat pump works differently. It extracts heat from the outside air, even in cold weather, and uses a refrigerant cycle and compressor to amplify that heat to a usable temperature. Think of it as a refrigerator working in reverse. Because it moves heat rather than generating it through combustion, a well-installed heat pump can deliver up to three or four units of heat energy for every one unit of electricity it consumes. This ratio is known as the Coefficient of Performance, or COP.
Installation Costs
A new gas combi boiler installation typically costs between two thousand and three thousand five hundred pounds depending on the brand, the complexity of the installation, and whether any pipework modifications are needed. If you are replacing a like-for-like combi boiler in the same location, costs tend to be at the lower end of that range.
An air source heat pump installation is a larger project. Costs typically range from eight thousand to fourteen thousand pounds before any grants are applied. This includes the outdoor unit, the indoor components, any necessary radiator upgrades, and the installation labour. However, the Boiler Upgrade Scheme (BUS) currently provides a seven thousand five hundred pound grant toward the cost of an air source heat pump, which brings the net cost much closer to that of a gas boiler for many homeowners.
Running Costs
Running costs are where heat pumps start to show their advantage. Because a heat pump delivers multiple units of heat for each unit of electricity consumed, the running costs can be comparable to or lower than a gas boiler despite electricity being more expensive per unit than gas. The exact savings depend on the COP achieved, which in turn depends on the quality of the installation, the insulation level of the property, and the flow temperatures used.
For a well-insulated home with appropriately sized radiators, a heat pump with a seasonal COP of 3.0 or above will typically cost a similar amount to run as a modern gas boiler. In some cases it will be cheaper. However, for a poorly insulated home where the heat pump has to work harder and at higher temperatures, the running costs may be higher than gas. This is why a proper heat loss survey is essential before committing to a heat pump installation.
The Boiler Upgrade Scheme (BUS) Grant
The BUS grant is available to homeowners in England and Wales who are replacing an existing fossil fuel heating system with a heat pump. As of the current scheme, the grant provides seven thousand five hundred pounds toward an air source heat pump installation. To qualify, your property must have an Energy Performance Certificate (EPC) with no outstanding recommendations for loft or cavity wall insulation. The installer must be MCS certified, and the application is made on your behalf as part of the installation process.
Which Properties Are Suitable?
Gas boilers are suitable for virtually any property that has a gas supply. They are compact, relatively affordable, and can be installed in a kitchen cupboard or utility room. This makes them the practical choice for smaller homes, flats, and properties where outdoor space is limited.
Heat pumps require outdoor space for the unit, which is roughly the size of a large suitcase or washing machine. They perform best in well-insulated properties where they can operate at lower flow temperatures, typically 35 to 45 degrees Celsius compared to the 60 to 70 degrees used by gas boilers. This lower flow temperature means that radiators may need to be larger to deliver the same heat output, or underfloor heating is an excellent pairing. Properties with solid walls, poor insulation, or very small radiators may require additional work to make a heat pump viable.
Pros and Cons at a Glance
Gas Boiler
- Lower upfront cost
- Quick and straightforward installation
- Works well with existing radiators and pipework
- Compact size suits all property types
- Relies on fossil fuel with a future ban on new gas boilers expected
- Running costs subject to gas price fluctuations
Air Source Heat Pump
- Lower carbon emissions and more environmentally friendly
- Potentially lower running costs with a good COP
- Eligible for the seven thousand five hundred pound BUS grant
- Long lifespan of 20 to 25 years
- Higher upfront cost even with the grant
- Requires outdoor space and may need radiator upgrades
- Best suited to well-insulated properties
Making Your Decision
There is no single right answer that applies to every home. If you live in a well-insulated property with adequate outdoor space, a heat pump is worth serious consideration, especially with the BUS grant reducing the upfront cost. If your home is older, poorly insulated, or lacks outdoor space, a modern high-efficiency gas boiler may still be the most practical and cost-effective option for now.
The best approach is to speak with an installer who is experienced in both technologies and can assess your specific property. We are both Gas Safe registered and MCS certified, so we can provide honest, unbiased advice on which system would deliver the best results for your home and budget.