Air Source Heat Pumps

Heat pumps can be a very efficient system for heating your home, and can be a long term solution to saving money on your energy bills. But how do they work, and why should you consider switching to one? In this guide we’ll introduce you to Air Source Heat Pumps, or ASHPs.

What is an air source heat pump?

An ASHP uses the air outside your property to heat the inside of your home. You can’t get a much better source of cheap energy than that!

The pump, a box resembling an air conditioning unit, is fitted to the outside of your house, usually at the side or back of the property. They can be ugly so normally aren’t placed above your front door!

This pump extracts heat from the air outside by drawing it through a fan, and uses this to warm a liquid refrigerant. The refrigerant is then compressed to further increase the temperature. The compressor uses a small amount of electricity.

This heated refrigerant in turn heats water which is pumped throughout the wet central heating system, into your radiators and/or underfloor heating. Any excess hot water can then be stored in a hot water cylinder, for use in taps and showers.

What types of air source heating can I consider?

There are two main types of Air Source Heat Pump. Air-to-Water pumps are the most common. They work as we outlined earlier, by using the air entering the pump to heat water in a wet heating system. This water is then the medium that heats up your home.

The second type, Air-to-Air, transfers the heat from the air into a refrigerant and then pumps out heated air through a fan. This type of ASHP is much more common in countries where complex central heating systems like radiators or underfloor heating are less standard, and generally where the average temperature is higher and doesn’t drop below freezing too often.

The type of ASHP you choose will be based on many different factors so It’s good to consider all your options when you compare energy deals. You may live in a very cold region where an Air-to-Air pump is inefficient, and equally you may struggle with Air-to-Water if your house isn’t already installed with a good quality heating system.

What are the pros and cons of an air source heat pump?

Pros

• In many cases, ASHPs will save you cash. This is even more likely if your current energy supply is a coal or electricity based system. Run an energy comparison with our tool to compare against your current deal.
• Most ASHPs are efficient for heating and cooling. You’ll be thankful to have one in the hot summer months as well as the depths of winter!
• ASHPs have a low environmental footprint, particularly when they’re used in conjunction with a renewable electricity source such as solar.
• ASHPs are very energy efficient.
• They are easier to install than a Ground Source Heat Pump, and most likely don’t require planning permissions, although it’s best to check this before installing.
• They remove any issues with the supply of fuel such as gas or wood deliveries.

Cons

• ASHPs produce less heat than traditional boiler systems. They often have to be running constantly in winter to maintain a good temperature in colder houses.
• For this reason an ASHP requires good insulation in your home. The pump will be next to useless in a draughty or poorly insulated building.
• They have lower efficiency in harsh climates than other heating sources. Below 0ºc efficiency drops off.
• ASHPs are also fairly noisy. When active the noise level is similar to that of low level traffic.

How efficient are air source heat pumps?

In many cases, very! They have a high Coefficient of performance (Energy output/ Energy Input) and a ready source of fuel, the air.

In certain conditions where the air temperature can get very low, Ground Source Heat Pumps are likely to be a better option as the ground temperature is more constant, and remains around 10ºc year round. For more information on Ground Source Heat Pumps, check out our guide. Heat Pumps, either Air Source or Ground Source, generally offer very high level of efficiency and often represent the best energy deals when you take into account long term savings.

ASHPS do, however, require electricity to run. This generally prevents them from being totally efficient. Coupling an ASHP system with solar panels or other renewable form of energy is a great way to increase efficiency even further.

What should you consider before installing an air source heat pump?

The main consideration for most people looking at heat pumps is the cost of installation. Pumps and the associated work to install them can range from £8000 to £15000 depending on the size of property and system installed. This is, however, considerably cheaper than Ground Source Heat Pumps usually come in at.

You should also be aware of how an ASHP will work with your current home insulation and heating system. Well insulated properties with underfloor heating offer the best possible conditions for a heat pump. For this reason ASHPs are most commonly installed in new build properties, rather than retro-fitted.

There’s also potential planning permission hang ups. These are less common for ASHPs than other forms of energy system though.

Lastly, check if installing an ASHP will actually save you money. A quick energy comparison can help you work out if these systems work out cheaper long term.