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For many, an air source heat pump (ASHP) is a great way to switch from fossil fuel heat to cleaner, greener heating, reducing your carbon footprint and energy bills at the same time. Although heat pumps have been used for decades in some areas of the world, the recent uptake in the Europe and UK has been spurred by the growing environmental and energy crisis.

It can be confusing sorting through all the misinformation when you’re exploring a technology different to the norm. We’ve debunked and explore eight common air source heat pump myths.

#1 You need underfloor heating for an ASHP

It is not necessary to install underfloor heating for an air source heat pump to work effectively although it can aid efficiency. As air source heat pumps work at lower temperatures, the essential requirement is to ensure any heat emitter, whether underfloor heating or radiators are matched to the heat needs of the property so they are designed to allow the heat pump to operate efficiently. This sometimes but not always requires radiator upgrades.

#2 You need space for a hot water tank

You will need a hot water cylinder to allow a heat pump to provide your hot water efficiently. Slim line cylinders are available  A second tank for heat storage is not always needed, although many systems can operate even more efficiently if they have one. This “buffer tank” or “accumulator” stores heat from the heat pump which can be used later for a quick heat boost if this is needed without the heat pump having to work less efficiently to provide this. You don’t need a hot water tank with a hybrid heat pump system.

#3 They don’t work in many types of homes

They can be installed in most property types as little outdoor space is required, so small or large, new or existing properties, rural or urban and even commercial properties can benefit from the energy-saving capabilities of a heat pump. Any system, whether a heat pump or a fossil fuel boiler, will use less fuel and operate more efficiently in a adequately insulated property provided the system of heat distribution (normally radiators) is properly designed to be matched to the property.

A recent survey of current heat pump users in the UK by NESTA has found that 81% of households were as satisfied or more satisfied with heat pumps compared with previous heating systems and this was higher in those with older properties at 83%.[1]

#4 They are noisy

Modern heat pumps are very quiet when they’re running, a similar level of noise to a domestic fridge, with a maximum output between 42 – 45dB. Heat pumps are positioned outside, making them less audible than a fridge which is indoors and on all of the time. This can make them slightly quieter than a traditional boiler – which can range from 48dB to 53dB, depending on your model. In summer, heat pumps won’t often be on when people are outside enjoying their gardens and as technology moves on they are getting even quieter.

#5 They are not as efficient as a modern gas boiler so it won’t make a difference to emissions

Heat pumps are more efficient than other heating systems because the amount of heat they produce is more than the amount of electricity they use.

The amount of heat produced for every unit of electricity used is known as the Coefficient of Performance (CoP). So a CoP of 3 means that for every 1kW of electricity the ASHP uses, it produces 3kW of heat. This is how a heat pump can operate at more than 100% efficiency. In ideal conditions air source heat pump operates at 300% efficiency or more, a COP of 3.5 is commonly achievable and ground source heat pumps can achieve even higher[2].

Traditional fossil fuel heating systems typically run at 84% efficiency. This means they produce less heat than the amount of fuel they use because some of the energy is lost.

This also means that, to provide the equivalent amount of heat, the greenhouse gas emissions from ASHPs are lower – even if the electricity is generated from fossil fuels.

ASHP how it works

#6 They don’t work when it’s cold

Tests show that heat pumps can continue to work effectively in temperatures as low as -16°C with ASHP technology a popular choice in both Norway and Sweden. Ostersund in Sweden sees an average temperature of -4°C to -9°C.[3]

They lose some efficiency as the weather gets colder however even a UK project substantiated the performance of heat pumps on Britain’s coldest days (where mean daily temperatures fell to as low as -6oC, significantly colder than the Isle of Man) and found only a marginal decline in whole system performance. The median ASHP system efficiency was 2.44 (or 244%) on the coldest days of the year, so maintaining very good efficiencies[4].

#7 My home needs to be fully insulated before getting a heat pump

It is not true to say that you cannot use a heat pump if a property is not well insulated. If your radiators, underfloor heating or the other forms of heat distribution are fit for purpose and they still put out enough power outputs at the lower operating temperatures that allow heat pumps to work efficiently, then they're just as adequate for heating a leaky building as any other heat source would be.

Once again, it is advisable, whatever the heating system, to install as many cost-effective energy efficiency measures as possible, such as insulation. Where there won’t be any further gains from fabric improvements a properly-designed and installed heat pump will still operate more efficiently than its fossil fuel boiler counterpart. Plus, bills will be higher in a property which is not as well insulated compared to a property which is well insulated.

#8 I need to install solar panels to have an air source heat pump

A heat pump is powered by electricity, which can come from the national network (the grid), from solar or other renewables, or a combination of both. It’s not necessary to have solar panels to have an air source heat pump. There is also solar assisted heat pumps on the market however theses are often not used for building heating although they could heat very small or thermally efficient homes, which have lower space heating requirements.







  • Air Source Heat Pumps
  • Myth Busting