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What’s an air source heat pump and how does it work?

Air source heat pumps generate energy from the ambient heat of surrounding air in order to provide a house with heat and hot water.

5 min read

Over the past year, gas prices have risen, making energy bills unaffordable for many UK households. Since there seems to be no guarantee that energy prices will go back down, it has become increasingly important to look for alternative ways of producing energy for domestic use.

Heat pumps have become one viable option to combat exorbitant energy prices, yet they remain overlooked and under-discussed.

This article will discuss one type of heat pump in particular: the air source heat pump. It will also cover questions around air source heat pump cost, as well as air source heat pump installation and air source heat pump grants potentially available to you.

What is an air source heat pump?

In general, a heat pump is a device that uses heat found naturally in an environment to provide more intense heat in a building.

An air source heat pump uses the surrounding air’s natural heat to work.

Let’s take a closer look at how air source heat pumps work.

How does an air source heat pump work?

Air source heat pumps need a system of pipes to work. These pipes are filled with a water and antifreeze mixture, antifreeze being a liquid that drastically lowers the freezing point of water.

With antifreeze, you can obtain a much colder liquid without it freezing and blocking the pipes.

Outside air, whatever its temperature, blows over the pipes. When the water-antifreeze liquid comes in contact with the air, it heats up and eventually evaporates.

The obtained gas is channelled through to a compressor, increasing the pressure and thus also the heat of the gas.

The hotter gas goes through a heat exchanger, which, with colder air or water, absorbs the gas’ heat. This is because heat is naturally attracted to the cold.

The heat transferred from the gas to the water is used to warm up your home -- the hot water can be used for radiators, underfloor heating or your taps.

The whole process is on a loop, as the refrigerant will then cool down, before being heated up again by new air.

Using an air source heat pump at home

An air source heat pump is most effective for underfloor heating, as the large surface area of such a system means that it doesn’t need to get very hot to provide heat. Radiators, being much smaller, require higher temperatures to be effective.

For your hot water needs, a heat pump produces slightly colder water than a boiler. If your water consumption is high, you might need a bigger water tank with your heat pump.

air source heat pump

Things to consider before investing in an air source heat pump

Pros of an air source heat pump

  • Efficiency: air source heat pumps produce heat and hot water at a much higher rate than traditional boilers.
  • Zero carbon: these heat pumps run on electricity, so if your energy supplier has a renewable tariff, your energy production is carbon neutral.
  • Running costs: air source heat pumps have low running costs, matching, or even lower than, traditional heating systems.
  • Boiler Upgrade Scheme: the government offers the option to receive a grant to replace your boiler by a heat worth, worth up to £5,000.
  • Installation: easier to install than their counterparts, ground source heat pumps (require digging trenches in on your property).
  • Maintenance: they are cheap and relatively easy to maintain, with a long lifespan (around 20-25 years).
  • Cooling: some air source heat pumps are multi-purpose, offering cooling during the warmer months.

Despite the many advantages of air source heat pumps, these systems do come with disadvantages.

Cons of an air source heat pump

  • Radiators: air source heat pumps are less effective with radiators, providing a less intense heat than a traditional boiler. Your radiators may only be warm to the touch.
  • Heat: despite being very efficient, these heat pumps will only provide ambient heating, and will not greatly increase the temperature of your house.
  • Insulation: heat pumps need a well-insulated building in order to be properly efficient. Check here to learn more about your home’s energy efficiency.
  • Installation: a long process, taking anywhere from 3 to 8 days
  • Space: heat pumps require a lot of space to function, for the air to circulate as well as the water tank.

What are the different types of air source heat pumps?

Air to air heat pumps

An uncommon option for air source heat pumps, the “air to air” options distribute hot air around a building.

These heat pumps don’t provide hot water -- being used only for heating -- but also double as cooling units (what we know as air conditioning).

Air to water heat pumps

The typical system used in the UK, in which air collected is transformed into hot water. This system provides both heating and hot water for your home.

How much does an air source heat pump cost?

Price

It is important to note that a heat pump is more expensive than a traditional boiler. Depending on the size of your heat pump, prices can range from £12,000-17,000.

Installation

Installing an air source heat pump is also expensive, coming in at around £11,000. Installation costs depend on your property, so it may be more expensive if your property needs alteration to fit an air source heat pump.

In response to these high costs, the government has offered a grant called the Boiler Upgrade Scheme, which can knock off up to £5,000 on the price of installation.

Running costs

Air source heat pumps really shine when it comes to running costs and efficiency. Whereas your traditional boiler has an efficiency of 90% (meaning that 10% of fuel is lost in the production of heat), air source heat pumps have an impressive efficiency of 350%.

Depending on your existing system, your air source heat pump could incur savings on energy bills:

  • Old g-rated boiler: replacing this system with an air source heat pump could reduce your bills by up to £1,400.
  • New a-rated oil boiler: an air source heat pump would actually represent a potential increase of around £330.

If you choose to switch to an air source heat pump, it is recommended that you also install an electric stove. Keeping a gas stove would add a costly gas bill.

Maintenance

Air source heat pumps last a long time -- around 20 years -- but should be checked on every few years by a professional. Maintenance costs, however, remain relatively low.

Which air source heat pump should I buy?

The ideal air source heat pump depends on your property, but here are some recommendations:

To sum it up

Despite expensive up-front and installation costs, air source heat pumps are an attractive alternative to famously inefficient boilers. These heat pumps are well suited to the UK’s moderate climate, needing only low temperatures to provide a building with ample heating.

Unlike boilers, which are subject to the ever-changing prices of energy bills, air source heat pumps maintain low and stable running costs. They also require less maintenance than a boiler.

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FAQs

Are there grants available for paying for air source heat pumps in the UK?

With the Boiler Upgrade Scheme, you may be able to receive up to £5,000 to install a heat pump.

Are heat pumps a renewable source of energy?

Since they require electricity to work, heat pumps cannot be considered as a renewable source of energy.

How efficient are air source heat pumps?

Much more efficient than boilers, air source heat pumps have an efficiency of 300%.

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