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Heat pump outdoors
03 Dec 2020

Are air source heat pumps really more energy efficient than boilers?

By Robin
  • Read time: 3 minutes
Air source heat pumps are a relatively new renewable heating technology that are getting homeowners to rethink the way they heat their home.

Most people cannot imagine another way of heating their houses besides the boiler. However, there’re a few new options available in the market such as the air source heat pumps, with promises of being more efficient, saving you money, and generally offering greener energy in order to make the earth more sustainable.

But are the air source heat pumps really more energy efficient than boilers? Continue reading to find out whether to buy the heat pump or boiler.


A boiler does exactly what the name suggests – it boils water. So, using fuel (normally natural gas) boilers heat water until hot. The hot water flows via pipes to the different radiators you’ve in your house that produce the heat, which warms your room. The common types of boilers available in the UK include:

Air source heat pumps

ASHPs (Air source heat pumps) are a far more current technology that is more complex or intricate, but ultimately performs just the same function as boilers. They use electricity to absorb latent heat from the air or ground in order to heat a house and hot water. Heat pumps can still absorb heat when ground or air temperatures are down to -25°C.

Since heat is simply absorbed and not generated, this heating method can offer up to four times the amount of energy it consumes. And so, this makes heat pumps an energy efficient heating method of your home. The 2 types of heat pumps are:

  • Air-to-water

  • Air-to-air

Why buy a heat pump instead of a boiler?


The average air source heat pump (ASHP) last for about 15 years, but there’re reports that ground source heat pumps and modern models have a lifespan of at least 25 years. The longevity is usually put down to their rigid or robust design – with just a few moving parts, there is little that can get damaged.

In comparison, most gas and LPG boiler’s lifespan is about 7 to 12 years.

Heat pump and boiler


The efficiency of a heating system corresponds to the volume of the energy it supplies, which is converted into valuable heat energy.

Old boilers are viewed to have 50 to 70 efficiency and so around a third to a quarter of the energy supplied to the boiler is simply wasted. But modern (oil, LPG, and gas) and biomass boilers have higher efficiency of about and above 90% mark.

On the other hand, ASHPs’ efficiency can reach up to 380%, with a coefficient of performance that measures 3.8.

ASHPs can attain high numbers since they absorb heat, which is found naturally outside and moves it inside.


A heat pump’s outdoor fan unit normally takes up the same space just as a regular washing machine.

Even though not always, it’s connected to an indoor heat exchanger or hydrobox that is the exact size as a conventional or regular boiler. Lastly, the hydrobox is connected to a hot water cylinder, like a gas boiler.

Ground source-style heat pumps need lots of pipe that is buried underground horizontally or vertically depending on your outside space. There is an indoor unit that can be as big as a regular boiler or as small as a box.

Gas boilers are thought to be more compact, mainly if you’ve a combination boiler or modern boiler designs that heat water directly from the mains supply. System boilers also need a separate hot water cylinder whilst regular boilers require both a feed tank and a hot water cylinder in the attic.

Heat pump outdoors


Boilers are cheaper upfront, but the ASHP will work out affordable long-term because of its longevity. And so, what is best for you largely depends on the priorities, whether short-term or long-term.

The larger upfront cost of an air source heat pump is also offset by the Renewable Heat Incentive (RHI) contributions and government grants such as the Green Home Grant Scheme.


A boiler requires annually maintenance checks at the very least from HVAC professionals to ensure safety or minimise the risk of carbon monoxide (CO) poisoning.

On the other hand, it’s recommended that a user to arrange for annual maintenance checks for an ASHPs, but it isn’t a requirement. Maintenance checks can prolong life expectancy and preserve high efficiency, but there are no serious consequences if you skip them.

User experience

Both heat pumps and boilers are now available with programmers, timers, automated as well as smart controls designed to aid you heat your house with efficiency and ease. The complexity of the heat system’s functionality will largely depend on the model and make you choose.

Unluckily, biomass boilers will need a little more effort, since you will have to manually fill them with wood pellets.


In spite of the efficiency of LPG, oil, and gas boilers rising to around 90%, ASHPs don’t burn any fossil fuels in order to generate heat.

A heat pump also uses very little electricity to perform, but its high efficiency makes it the far more climate-friendly option. If the electricity running the pump is generated through wind farms or solar energy instead of coal this is better because carbon emissions would be minimal or zero.

A biomass boiler is also an environmentally friendly choice worth considering. Since it burns wood, it is only emitting the exact amount of carbon emissions, which was extracted, so it is technically carbon-neutral.

ASHP vs boilers

The bottom line: ASHP VS Boiler

A heat pump is probably your best option, if you aren’t connected to the mains supply, want generally less expensive bills with no or less maintenance, are constructing a sustainable property, or want to have an eco-friendly life.

If you can’t afford the cost of a ASHP or you’re still connected to the mains gas supply, you can still decrease heating costs and carbon emissions by replacing the traditional boiler with a higher efficiency and modern boiler.


Written by Robin

Writes blogs about e-mobility and climate solutions for 50five.