Air Source Heat Pump vs. Gas Boiler

Gas boilers and air-source heat pumps are two common heating options, but the right comparison depends on the property, its heat loss, existing emitters, hot-water demand, energy tariffs and the quality of the proposed system design.

However, in the other corner, you've got the rising star of the heating system world: the air source heat pump. By extracting heat from the outside air, the heat pump can warm your entire home and provide you with hot water, without relying on any fossil fuels to do so.

In this article, we'll pit the two forms of heating against each other, discussing efficiency, cost, and environmental impact. By doing so, we'll help you decide which of the two options is best for your home.

A gas boiler burns fuel and transfers the resulting heat to water for radiators, underfloor heating and hot water. Combustion products leave through the flue, so installation, ventilation, maintenance and carbon-monoxide safety requirements are important.

• Quick heat: It doesn't take long for a gas boiler to provide your entire home with heat.

• Consistent heat: The heat provided by gas boilers is consistent and won't vary unless you change the thermostat yourself.

• Durable: Gas boilers tend to last around 10-15 years, with performance levels staying high depending on maintenance.

• Expensive to run: The ever-fluctuating cost of fossil fuels makes gas boilers expensive to run, often leaving poorer households with the decision of whether to eat or heat the home.

• Direct combustion emissions: Gas boilers emit CO2, which becomes trapped in the atmosphere, heating up the planet. They also use fossil fuels, which can't be replaced, unlike renewable energy.

• Carbon monoxide leaks: If your gas boiler breaks down, it can emit carbon monoxide, a poisonous gas, which will prove fatal if undetected.

It's important to note, gas boilers are now being phased out, with new-build homes being made to install low-carbon alternative heating systems instead.

An air-source heat pump uses electricity to move heat from outside air into a water-based heating system. Most domestic systems use an outdoor unit with refrigerant and indoor hydraulic components; the exact arrangement depends on the selected product and hot-water design.

While heat pumps require electricity to run, they don't burn any fossil fuels while heating your home. Instead, they rely only on the outside air, a renewable source of energy.

• Efficiency: A well-designed heat pump can deliver several units of heat for each unit of electricity consumed, but seasonal performance changes with outdoor temperature, flow temperature, controls and installation quality.

• Carbon neutral: As they don't burn fossil fuels, air source heat pumps are ideal for lowering your carbon footprint and moving towards a greener future.

• Cost considerations: Running a heat pump requires electricity, and solar panels do not guarantee that heating costs will be fully covered. Compare the expected annual electricity demand and current tariff with the existing system on the same assumptions.

• Installation costs: Heat pump installations can be expensive. However, with the UK Government's Boiler Upgrade Scheme (BUS), you can save up to £7500 on the installation.

• Space requirements: Air source heat pump units will require you to have adequate room for both the outdoor and indoor units.

The differences between heat pumps and gas boilers are stark, from an environmental, cost, and efficiency perspective. Let's take a look at the main differences:

Neither technology should be selected from a generic comparison alone. A heat pump can be a strong lower-carbon option when the building and emitters support efficient operation, but comfort, running cost and installation scope should be modelled for the individual home.

Plus, with the government schemes and initiatives on offer, upgrading to a heat pump from a gas boiler has never been more affordable.

There's also the long-term financial gains to think about. Running-cost comparisons depend on the heat pump’s seasonal performance and the relative electricity and gas tariffs. That's because your heating will be provided by the air; a 100% renewable energy source.

Overall, the benefits of air source heat pumps vastly outweigh the benefits of gas boilers in 2025. Heat pumps are built for the future, with the aim of making our planet greener and safer to live on.

• Use a room-by-room heat-loss calculation.

• Record the proposed flow temperature and any radiator or underfloor-heating changes.

• Compare annual heat demand, system efficiency and current tariffs.

• Include hot-water storage, electrical work, controls and maintenance.

• Check available grants separately from the full installed price.

• Ask for the expected comfort and running cost assumptions in writing.