A Guide to Air Source Heat Pump Efficiency

heat pump on the wall

Air source heat pumps have a typical efficiency rating of 400%

That’s at least four times better than all gas boilers

They can achieve that level of efficiency without polluting the planet


The future is bright for air source heat pumps.

Their efficiency is miles ahead of gas boilers – which will be banned in newly built houses from 2025 – and they’re renewable, as they’re purely powered by electricity.

Their cost is also coming down, particularly as the government’s Boiler Upgrade Scheme is providing homeowners with a £5,000 discount if they replace their gas boiler with a heat pump.

We’ve delved into exactly how much more efficient air source heat pumps are than other heating systems, and what makes them so much better.

heat pump on the wall

How efficient are air source heat pumps?

Air source heat pumps typically have an efficiency rate between 350% and 450%.

This means that on average, your air source heat pump will produce an outstanding four units of energy for every unit of electricity it absorbs.

To put this in context, the average UK home uses just over 12,000 kWh per year for heating, and your heat pump would be able to provide the same amount of heat from just 3,000 kWh.

In comparison, electric boilers are four times worse – with an efficiency rate of 100% – while the best gas boilers can only reach 98% efficiency.

Electricity is usually five times more expensive than gas, which negates any gains you’d make from your heat pump’s incredible efficiency – but the times are changing.

With gas prices on the rise, and electricity fast becoming the best way for the UK to reach its goal of net-zero emissions by 2050, you’d be investing in a future that’s almost here – and which will save you an enormous amount on your heating bill when it does arrive.

Why are air source heat pumps so efficient?

Air source heat pumps are four times more efficient than gas and electric boilers because they don’t have to burn fuel or painstakingly convert electricity into heat.

Instead, they simply transfer warm air from outside to inside your home, by allowing it to blow through the compressor and heat exchange, where it’s automatically turned into hot water.

You can work out how efficient any given model is by looking at its Coefficient of Performance (CoP) – though you should check the Seasonal Performance Factor (SPF) for a full picture.

While the CoP tells you a machine’s peak efficiency, the SPF tells you the heat pump’s average efficiency over the course of an entire year.

How efficient are ground source heat pumps?

Ground source heat pumps are 300% to 400% efficient, according to the Ground Source Heat Pump Association.

This puts these machines, which draw warmth from at least a metre below the Earth’s surface, squarely in the same ballpark as air source heat pumps.

Some models are more efficient than their air-based cousins, while others fall short – it’s all down to the individual heat pump, and its capabilities.

How efficient are air source heat pumps in winter?

Air source heat pumps are around 20% less efficient during winter, because they need more electricity to draw the heat from the air.

This still makes them at least three times more efficient than gas boilers – even when it’s snowing outside.

And you don’t need to worry about your air source heat pump breaking down at any point, even if the temperature falls below freezing.

Modern heat pumps continue working when it’s as cold as -10°C, and the best models will still keep you warm even when it’s -25°C outside.

That’s because there’s still heat in the air at this point. For there to be no heat at all, it would have to be -273°C – and even the worst British winters don’t get quite that bad.

During the winter, you might need to carry out maintenance checks more regularly, since the weather typically gets worse during these months.

In areas with extreme weather during the cold months, homeowners could consider getting a heat pump cover, which guards the outside unit against debris and snow.

Are heat pumps more efficient than gas boilers?

Yes, heat pumps are much more efficient than gas boilers.

Air source heat pumps’ efficiency ratings are typically 420% better than gas boilers’ ratings – and this figure can go as high as 530%.

Ground source heat pumps can get just as high in the efficiency stakes, but are usually around 370% more efficient than gas boilers.

Heat pumps’ obvious superiority here comes from their ability to produce about four units of heat for every unit of electricity they’re given, whereas their fossil fuel-powered counterparts produce about 0.95 units of heat from one unit of gas.

What’s the most efficient air source heat pump?

The most efficient air source heat pump is currently the catchily named Hitachi Yutaki M RASM-4VNE, according to our rating of the best heat pumps of the year.

This wonderful machine has an efficiency of 500%, meaning it produces five units of heat for every unit of electricity.

Hitachi’s market-beating model produces 11 kW of heat, which is more than good enough for the average house, and will even provide enough heat for a 200 m² home.

It can also be purchased for around £4,260, which is a bargain – and would be covered by the government’s Boiler Upgrade Scheme.

Next steps

If you like the sound of what you’ve read so far, your next move is to do some research to see which model would suit your home.

Look through our best air source heat pumps to check whether any of the top machines would work for you – and when you get your new heat pump installed, make sure your chosen company uses the Boiler Upgrade Scheme to get you a discount of at least £5,000.

Josh Jackman Senior Writer

Josh has written about eco-friendly home improvements and climate change for the past three years. His work has featured on the front page of the Financial Times; he’s been interviewed by BBC Radio; and he was the resident expert in BT’s smart home tech initiative.

Back to Top