green energy air source heat pumps

Air Source Heat Pumps: Everything You Need to Know

03 May 2021

What is an Air Source Heat Pump?

An air-source heat pump works by drawing in outside air through the unit and converting it to heat using a refrigeration process, which can be used to provide heat for radiators, underfloor heating and domestic hot water.

There are two kinds of air source heat pump:

  • Air to water heat pumps - which absorb heat from the outside air and transfer it through a central heating system to supply radiators, underfloor heating systems and domestic hot water cylinders.
  • Air to air heat pumps - which absorb heat from the outside air at temperatures as low as -15°C, and transfer it into heat in home using fan convector heaters.

They’re incredibly energy efficient and typically produce 3 - 4kW of heat energy for every 1kW of electricity used to power them, saving you money on bills and cutting energy consumption.

Air Source Heat Pumps don’t produce any harmful emissions unlike carbon based fuels such as Natural gas, LPG, Oil and solid fuel, so are much better for the environment.


The Advantages of an Air Source Heat Pump

Some of the advantages of using an air source heat pump include:

  • Significantly lowering your carbon footprint through energy savings
  • Highly efficient, saving you money on your bills
  • They are eligible for the governments Renewables Heat Incentive payments
  • Some models can provide heating and cooling
  • They can work in temperatures as low as -15°C
  • The installation process is reasonably straight forward
  • They’re low maintenance
  • They have a long lifespan
  • There is no fuel storage required
  • They do not produce products of combustion so are extremely safe
  • They can be supplemented by solar panels or even wind energy
  • High-Temperature models available to retrofit to existing radiators
  • Low-temperature models available which are ideal for underfloor heating or if the radiators are being upgraded or are already oversized


Some Disadvantages of an Air Source Heat Pump


  • Don’t work as well in poorly insulated homes
  • The up-front cost will be more than a like for like boiler swap
  • Often require a new hot water cylinder designed for Heat Pumps
  • Low temperature models require an immersion heater to top up the hot water temperature
  • Low temperature units take a little longer to initially heat a room compared to a gas or oil boiler.
  • They work less efficiently in lower temperatures but will still work to -15 degrees.
  • The outdoor unit contains a fan and a compressor which do create a low-level humming noise
  • They require electricity to run


Air Source Heat Pump Grants

If you decide to buy an air source heat pump, you’ll be eligible to receive government support payments as part of the Renewable Heat Incentive (RHI)

In order to be eligible for the grant, you have to have an air-to-water heat pump.

Payments are made quarterly, over a 7 year period and are based on the projected energy produced by the Heat Pump up to a pre-capped amount. The amount of RHI payment available can often cover a substantial portion of the initial cost of installation.

As we are MCS (Microgeneration Certification Scheme) and Trustmark certified, Hales & Coultas are qualified and approved to install Air Source Heat Pump systems and can guide and support you through the RHi application process.

Our friendly team are always available if you need help or advice with your applications or any other potential funding options.


Is an Air Source Heat Pump Right for You?

A few things to consider when working out whether an air source heat pump is right for you are:

  • What fuel you’ll be replacing it with - air source heat pump systems are more likely to pay for themselves quicker if they’re replacing an expensive to run system like electric storage heaters, solid fuel, LPG and oil. The savings will be less when compared to a modern gas condensing boiler but with zero emissions, they are much kinder to the environment.
  • Whether you have somewhere to put it - it’ll need a space usually on or near an external wall where a unit can be sited either wall-mounted or placed on the ground, and it will need a clear flow of air.
  • Whether you have the right heating system – Heat pumps require a wet central heating system provided by radiators or with underfloor heating. 
  • How well insulated your home is – It makes sense to insulate your home as well as is reasonably possible, regardless of the type of heating you have, but air source heat pumps work best when they’re producing heat at a lower temperature so to maximise the benefits, the better insulated your home is, the better the results
  • If you don’t have room for a domestic hot water cylinder, we can design and supply a hybrid or bi-valent system that can link to an existing gas or oil combi boiler.


Air Source Heat Pump Installation

Before the installation, Hales & Coultas will carry out a full internal and external survey of your property, measuring each room in order to work out the heat requirement and radiator sizes for each room.

We will discuss and agree with you a suitable location to install the outside unit.             

Some systems only require an outside unit (Mono-block) and some systems require an inside and outside unit (Split system) so would also require some space inside if the split system is used. The inside unit is similar in size to a traditional wall mounted gas boiler.

We would discuss the full range of options with you to ensure our design best meets your requirements.

Most new systems will require a new hot water cylinder designed for use with a Heat Pump so this would just replace the existing one.

Connecting to the existing heating system is relatively simple and any upgrades required to the system or radiators would be identified at the survey.

The outside unit will require a new electric supply direct from your consumer unit/fuse-board.

New efficient user controls and new electrics would complete the installation. 

All work is installed and commissioned to MCS standards. 

2-5 year parts and labour warranty available.


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