There are various ways to heat a home, from gas-fueled furnaces to boilers and solid fuel appliances, but source heat pumps such as air source heat pumps are becoming more common in a world where net zero carbon targets are being sought and fossil fuels being phased out.
An air source heat pump is an appliance that helps to provide heating for an internal space using the warmth stored in outside air, but may also provide cooling depending on the type. Air source heat pumps can also be used with water heater storage tanks to provide domestic hot water.
We’ve been using an air source heat pump to provide domestic hot water and central heating for our own home for several years.
We discuss further in this article more about what air source heat pumps are, using our own heat pump system as an example, as well as what they do, some of their advantages and disadvantages, and whether it can be worth investing in one.
What Is An Air Source Heat Pump?
Air source heat pumps are appliances that are installed on the outside of a building and can typically look much like larger air conditioning units. An air source heat pump will be connected to internal components in a building, either in the form of ducts or through a series of pipes that join up with a central heating system.
Air source heat pumps (ASHP for short) are typically rectangular or square mechanical and electrical units that are found installed on the outside of a building.
Our air source heat pump is located on the side of our house and installed just off the garage wall.
It’s mounted directly onto the ground and has pipework located out the back of it heading through the garage to the water heater tank in the utility room.
Air source heat pump units themselves can often look like larger types of air conditioning units and the image below shows our heat pump sat next to a domestic air conditioning unit for comparison.
See our article where we compare air source heat pumps against air conditioning.
An air source heat pump extracts heat from the outside air as it passes through a heater exchanger within the unit. This warmth is transferred inside a building through refrigerant in pipes or air ducts used for central heating and domestic hot water if required.
Air to water source heat pumps (like the one we have) are frequently used to provide indoor heating when paired with a central heating system, along with radiators and/or underfloor heating.
An air source heat pump unit will pull outside air through the back using a fan and force the air over a heat exchanger.
This heat is absorbed by the refrigerant travelling through the unit (even at very low temperatures), before being compressed to provide further heat and sent inside to be extracted for use with a central heating system and/or hot water.
Air to air source heat pumps can work in similar way but can use ducts to transfer warm air around a building.
Air source heat pumps can also potentially be used for cooling purposes when used with a reversing valve to remove heat from a home, rather than to heat a home.
See our guides of how an air source heat pump works and the differences between air to water and air to air heat pumps for more in-depth information.
Air source heat pumps won’t be able to provide the same instantaneous heat that a traditional gas furnace/boiler can and so are best suited for use in a well-insulated spaces (such as modern homes) and used with larger-sized radiators and underfloor heating (radiant floor) helping to provide a greater surface area for the heat to be released over time.
Air source heat pumps are excellent to use in wider areas that require less temperature intensity, and why they are often preferred as an underfloor heating system.
The reason for this is the pump’s lower energy output when compared to its alternatives, which makes it a better option for slower, longer, and more sustainable temperature adjustments.
Our home uses both a mix of underfloor heating and large radiators to release the heat provided by our air source heat pump more gradually over time.
Air source heat pumps can still be retrofitted and used in holder homes however.
ASHP’s are therefore ideal for those living in milder climates (like here in the UK), where the difference between outside and inside temperatures isn’t typically too extreme.
If used in much hotter or colder areas, they may need to work above their ability to regulate the space’s temperature, making them prone to premature defects and failure.
These pumps can be remarkably efficient in some conditions while helping you save on your energy bills in the process.
On the other hand, they can often required to be paired with a backup heating system, as in more extreme conditions, they may not always be able to provide the needed output for adequate temperature control.
As an example, our system using an immersion heater within the hot water tank to ensure that very hot water is always on demand, but is only used when required.
Air to water air source heat pumps (that utilize refrigerant in pipes) can be used to provide heat for a building or home, but air to air source heat pumps (that move air through ducts) may also be able to provide cooling (air conditioning) during warmer months.
Air to air source heat pumps therefore can’t provide domestic hot water for a home, but air to water source heat pumps (like ours) can. See our articles on using an air source heat pump with a tank and using an ASHP to provide domestic hot water.
Installing an air source heat pump can come with a range of benefits including lower carbon footprints and a more sustainable way to heat your home.
However, the upfront costs associated with installing an air source heat pump and all the other necessary equipment can be quite high, which is one of the major downsides of such systems.
Air source heat pumps provide heat from a renewable energy source, which can help outweigh all the typical high initial installation expenses.
Compared to more conventional alternatives, especially old and inefficient heating appliances, air source heat pumps can consume less energy/fuel for the same output as their counterparts, often making them more cost-effective.
ASHP’s provides an eco-friendly alternative that allows you to heat your home, using only use outside air to provide temperature control. When the electricity used to power the heat pump also comes from a renewable energy source, an air source heat pump can be a very sustainable heating system.
Air source heat pumps are very versatile compared to other systems. You can use them for both heating and cooling purposes depending on the type of heat pump and on your preferences. These systems may also be used to heat running water, as well as your living space, potentially saving you even more money.
These heating systems may be one of the most low-maintenance options in the market today. The installation process can be straightforward, and on average, it can requires only a couple of days to install.
To install a pump, you won’t typically need to make any structural changes to your space as it will be mounted outside, and you usually wouldn’t need planning permission, although the latter may depend on your local laws and regulations.
When it comes to maintenance, an air source heat pump only requires a thorough inspection by a technician about once a year. Having said that, frequently conducting checks and clean-ups yourself could significantly increase the lifespan of the equipment. This level of maintenance can help your system work efficiently for upwards of 20-25 years.
We have our air source heat pump and water heater tank serviced annually in line with the manufacturer’s guidelines.
Not only can you save on your electricity bills implementing an air source heat pump, but you may also be able to get paid for the renewable heat you’re producing or for replacing an existing system with a heat pump.
This can include the Boiler Upgrade Scheme that’s currently being offered in the UK.
An air source heat pump doesn’t offer always quite the same heat output than alternative options, meaning that you’ll need to extract the heat over a longer period of time to get the same effect.
This means you will need a well-insulated home and a larger heat-emitting surface when using this system, as opposed to their gas boiler counterparts. Therefore, you’ll need bigger radiators to control the temperature of the same-sized space when using an air source heat pump, or use underfloor heating in addition or instead of radiators.
Our air source heat pump was installed brand new with the house and so the heating system was designed with the heat pump in mind, but upgrades to existing heating systems may be required when retrofitting one.
When temperatures reach below 32°F (0°C), an air source heat pump can slowly start to lose its heating capabilities.
This is because the equipment uses outdoor air to produce heat; Lower outside temperatures mean that it must work harder to extract the heat from the air.
However, energy is still present within the air even at low temperatures and the heat stored in the air at -18°C is still 85% of the energy stored at 21°C.
The manual for our air source heat pump states that is has a guaranteed operating range for heating of between -20 to 21°C, and so air source heat pumps can work at very low temperatures if required.
You can expect to have high initial costs when first installing an air source heat pump and any other necessary central heating upgrades.
The actual costs can depend on your existing system and whether upgrades are required to the radiators, pipes or underfloor heating that serve your current setup.
In order to work as efficiently as possible, an air source heat pump needs to operate in an already well-insulated space. This means that you may need to invest to properly block any possible temperature circulation between the outside and inside area before installing.
See our complete guide on all the pros and cons of air source heats pumps for more information.
Buying an air source heat pump is worth it if you have a spacious, well-insulated house located in a mild climate, as it provides diverse forms of eco-friendly energy at a low cost. On the other hand, they require high initial investments and are less efficient if you live in more extreme climates.
Air source heat pumps are an excellent, low carbon footprint way to control the temperature of your living space.
They work more efficiently in well-insulated homes with underfloor heating systems. Although this option offers many excellent advantages, it’s not always ideal to use in colder or hotter climates, where there is a notable difference between the outside and inside temperature.
Therefore, deciding on whether an air source heat pump would be ideal for you comes down to your house’s qualities and location, as well as your budget. Speak to an installer to get their view on your situation.