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Unraveling the Mystery of The Air Source Heat Pump


Unraveling the Mystery of The Air Source Heat Pump

Discover the mechanisms behind air source heat pumps, including their benefits and potential drawbacks upon installation.

An air source heat pump serves as a revolutionary method to heat your home. It allows you to produce your own sustainable heat and may potentially reduce your energy costs over time.

These pumps distribute heat at a lower temperature compared to conventional gas and oil boilers, necessitating longer operational durations to maintain your home's comfort levels.

It is crucial to have an adequately insulated home. Without it, the heat produced by the pump can easily escape, resulting in insufficient heating levels.

The potential for significant heating bill reductions is greater when replacing an expensive system such as electric storage heaters, oil, liquefied petroleum gas (LPG), or coal.

Advantages and Disadvantages of Air Source Heat Pumps: A Closer Look Air source heat pumps offer low-maintenance heating and hot water provision. However, they are not without certain limitations. Here are their primary pros and cons:


  • Highly efficient as they produce more energy than they consume. For example, with a Coefficient of Performance (COP) of 3.0, 1kW of consumed energy translates to 3kW of heating energy. The efficiency is contingent on system design, sizing, heat loss, and weather conditions.
  • Emit less CO2 compared to traditional heating systems
  • Easier to install than ground source heat pumps, particularly in retrofit situations
  • Potential for heating cost savings compared to older systems, possibly resulting in lower operating costs than gas boilers


  • Require substantial outdoor space for the external condenser unit
  • Condenser units may be loud and emit colder air around them
  • Require electricity, thereby not entirely carbon-neutral (unless powered by renewable sources such as solar panels or wind turbines)
  • May necessitate new, larger radiators or underfloor heating system compatible with lower water temperatures
  • Installation demands careful design and calculations to ensure comfortable heating and manageable bills. An MCS certified installer is necessary

Understanding the Functioning of an Air Source Heat Pump

The operating principle of an air source heat pump involves capturing heat from the air, amplifying its temperature using a compressor, and channeling this heat to your home's heating system.

Much like a reversed refrigerator, an air source heat pump:

  • Absorbs outdoor air heat into a liquid refrigerant at a low temperature
  • Elevates the refrigerant's temperature by electrical compression, subsequently condensing it back to liquid form to release the stored heat
  • Distributes the heat to radiators or underfloor heating, with surplus heat stored in a hot water cylinder
  • Uses this stored hot water for showers, baths, and taps
  • Consumes electricity but uses less electrical energy than the heat it generates, thereby enhancing your home's energy efficiency

Air source heat pumps can function efficiently even at sub-zero temperatures.

Similar to air source heat pumps, ground source heat pumps extract and amplify natural heat to warm your home. Discover how ground source heat pumps operate.

What is an Air Source Heat Pump?

An air source heat pump is a sustainable heating solution that captures external air heat to elevate your home's temperature.

These heat pumps resemble air-conditioning units, with their size being proportional to the required heating output—the more the heat needed, the larger the pump.

Air source heat pumps come in two variants: air-to-water and air-to-air, each compatible with different heating systems.

Air-to-Water Heat Pumps

Air-to-water heat pumps draw heat from the outdoor air and transfer it to your central heating system. They pair well with larger radiators or water-based underfloor heating due to the comparatively cooler heat produced.

Including larger radiators or underfloor heating during home extensions or new construction simplifies the process and is often more cost-effective than later retrofits.

Air-to-Air Heat Pumps

Air-to-air heat pumps take external heat and disseminate it through fans. A warm air circulation system is needed to distribute the heat throughout your home.

They cannot generate hot water, necessitating a separate water heating system. However, during summers, these pumps can operate in reverse, acting as air-conditioning units to cool your home.

Installing an Air Source Heat Pump

Typically positioned outdoors, air source heat pumps need sufficient space for air circulation. Indoor units contain pumps and hot water.

They are less disruptive to install than ground source heat pumps, eliminating the need for garden excavation. Although planning permission is generally not needed, residents of listed buildings or conservation areas must obtain local authority consent. Compliance with regional building regulations is essential.

It's important to ensure proper home insulation for efficient heat retention. Underfloor heating or larger radiators are usually installed to better distribute the heat.

After the system's completion, a Commissioning Certificate from the installer and a Microgeneration Certification Scheme (MCS) installation certificate is provided, essential for most funding schemes.

Are Air Source Heat Pumps Efficient?

A typical heat pump should offer a 250% - 300% efficiency, generating 2.5 - 3 units of heat for each unit of consumed electricity. The Seasonal Coefficient of Performance (SCOP) provides an average efficiency across the entire heating season, factoring in warm, mild, and cold days.

Your installer should provide a practical view of costs and efficiency by estimating the SCOP before installation. Regular servicing every two to three years and routine grill maintenance are necessary.

Air source heat pumps can contribute to a reduced carbon footprint as they utilize a renewable heat source, air. However, they require electricity, resulting in some CO2 emissions.

Energy Labels on Heat Pumps All heat pumps must display an energy label indicating their efficiency, ranked from dark green (most efficient) to red (least efficient). As of 26 September 2015, new heat pumps must have an EU product label, and the installer must produce a package label reflecting the efficiency of multiple heating system components.