Are Air Source Heat Pumps A Real Alternative?

What Is An Air Source Heat Pump?

An air source heat pump is a mechanical unit (like an air-conditioning unit you see when you go on holiday!) that usually sits at a pre-determined location outside your home or property.

There are 2 main types of air source heat pumps (ASHP):

1. Air-to-water system
2. Air-to-air system

An air-to-water source heat pump works by transferring heat from the outside air to water, which then heats your rooms via underfloor heating or radiator, otherwise known as your wet central heating system. It can also heat water stored in a hot water cylinder for baths, showers and hot taps.

An air-to-air setup starts in the same way, transferring the heat from air outside but this time around it transfers that air to ducting which supplies the heat via a fan outlet to heat rooms directly.  It can work in reverse by supplying cool air in the summer months, not that we need that much in Scotland!  It’s worth noting that these systems won’t supply hot water like an air-to-air setup so an alternative like a hot water cylinder with an electric immersion heater will be required.

How does an air source heat pump work?

To make it easier to understand the inner workings, it is sometimes helpful to think of the ASHP as a fridge working in reverse!

Air source heat pumps absorb heat from the air outside into a fluid called a refrigerant.  To then increase the temperature of this fluid it needs to be compressed (thermodynamics), this is then transferred through the heat exchanger to heat the water. This then provides heating and hot water to your home.

Heat pumps can extract heat from air temperatures as low as -15 degrees Celsius, providing heating and hot water all year round. The only electricity used by the heat pump is to run the compressor and circulating pump. This allows it to transfer more heat into your home than it takes to run.

Are air source heat pumps cost effective?

You may now be considering the cost of the setup and additionally, the cost to run.

The cost of an air source heat pump can vary depending on the size of the heat pump, the size of your property, and whether you need to change how you distribute heat around your home.  The best time to consider installing these types of systems would be when you’re already renovating or extending so that installation costs can be kept lower.

When it comes to considering the cost of running an ASHP this can be a whole other subject on its own so we will make it super simple. 

This is based on 3 main factors:

1. The COP of the unit (coefficient of performance)
2. The heat requirement for your property
3. The outside temp of the heat source itself

Generally speaking, an ASHP will be cheaper to run if you’re purely using it for space heating (as your central heating system) compared to an A-rated Gas Boiler.  If it’s also used for hot water then it tends to be more expensive to run and the main reason for this is the maximum heat it can generate.

Air Source Heat Pumps generally produce a maximum heat of 50 degrees Celsius and to bump that figure up, to say 60 degrees, more electricity will be needed to heat the water and therefore running costs increase.  

To make it more appealing, the Government have to come up with a way for more people to transfer to this type of energy generation and therefore you can reduce the cost to you through a Government grant.

Can the air source heat pump heat hot water?

It’s a valid question and boggles the mind how air heats water, especially at higher temperatures like 50 degrees…

The simple answer is YES.

Through the process described above where the latent heat from the air is taken from outside, compressed (heating it up) and then exchanged/passed heat to warm the water within a cylinder tank.  The water contained within your water tank will heat up over time and will be ready when you need it.  You will of course have to bear in mind that the water will fill with cold water which will then need to be heated once more.

This is the main difference between an air source setup and a combi boiler as the latter gives you hot water on demand.

Do air source heat pumps work in cold weather?

It’s fair to say “but if it works by taking the heat out of the air, how will it work in cold temperatures”?

Air Source Heat Pumps operate at optimal levels down to around 7 degrees Celsius.  As the temperature drops the heat pump has to work harder to heat that air (use more electricity) but it can do this down to -15 degrees Celsius and still work fine.

So yes, it does work in cold weather but it’s not as efficient as when outside temperatures are higher.  Technology is always advancing so no doubt it will become more efficient over time.

How much is an air source heat pump?

It’s fair to say you will pay more for an ASHP than you will for a gas boiler.  

Typical setup costs can range from £6000 to £15000 but we can narrow this figure down when we come to assess your property.

Although when you compare it to a Ground Source Heat Pump which can cost between £22000-£30000, then you might see why they tend to be the preferred choice when considering heat pumps in general.

As the demand for ASHP goes up along with the supply and as the Government pushes their agenda towards net zero, then it’s safe to say this should drive the price down.

Summary Of Air Source Heat Pumps

It’s safe to say there’s a lot to consider when thinking about whether or not you should consider installing an Air Source Heat Pump for your home or property.

They are definitely going to be a thing of the future as the whole world tries to get rid of their addiction to fossil fuels.  Although new technologies around hydrogen gas as a fuel could become a player within our gas boilers.  Boiler manufacturers are making sure they work with both natural gas and hydrogen as they will see the rising demand for ASHP’s as a threat to their business which is understandable.

Generally speaking, if your property is well insulated, setup to integrate with an ASHP setup or you’re about to embark on redevelopment work then it’s definitely worth checking them out.

We hope you found this article of value.  SmartGas does not actually supply or install ASHP’s, it’s something that is on our radar.  We appreciate that customers want a choice when heating their homes and we want to train up our engineers to be able to offer this service in the future.  As you will appreciate this may take some time but we will update our site when that time comes.