Air Source Heat Pump Disadvantages & Advantages

In the UK, over 17 million homes use gas boilers for heating, resulting in the emissions of thousands of tonnes of carbon each year, a major cause of climate change. In a sour twist of irony, heating our homes is heating the planet, too. 

Currently, domestic heating accounts for around 14% of the UK’s total emissions, placing it in direct conflict with the government's legal obligation for carbon neutrality by 2050. 

Low-carbon alternatives such as suffering through the cold, hydrogen boilers and heat pumps offer a (more or less) viable solution to this problem, providing homes with a greener, more reliable and more convenient heating option. 

Ready to make your home more energy-efficient and cut down on your heating bills? Get a heat pump quote today from our trusted partners at Heat Geek here.

What is a Heat Pump? 

The Committee on Climate Change has estimated that 19 million heat pumps will need to be installed to meet the commitment to reach net zero by 2050. So are going to play a big part in the decarbonisation of heating in the UK. 

As their name implies, heat pumps effectively pump heat from one location to another. They achieve this by extracting heat from the air outside of your home or from the ground and using it to warm your home. If that sounds impressive in itself, remember they do so when it’s cold outside. 

There are three main types of heat pumps:

• Air source heat pumps

• Ground source heat pumps

• Hybrid heat pumps

They work by absorbing heat from the air, ground or water and can provide both central heating and hot water, while hybrid heat pumps can use a boiler to provide additional heat when the weather is exceptionally cold.

Heat pumps do require small amounts of electricity to operate and combined with the fact that they take the heat from the environment, they are incredibly efficient.

If AI isn’t taking over your job, perhaps your heat pump could, with that efficiency.

Unfortunately, air source heat pumps cannot provide the same, consistent heat output as gas boilers, so alone are unsuitable for many applications.

For example, they are typically installed together with an underfloor heating system and in modern energy-efficient properties that are very well insulated and with families that consistently close the door when they’re asked to - that may or may not exclude your kids. 

Where a heat pump alone can not meet heating demands, a hybrid option, which works in harmony with a traditional gas boiler can be considered. 

See how hydrogen boilers compare with heat pumps in our heat pump vs gas boilers article. 

Different types of Heat Pumps 

There are three major types of heat pumps in the UK, all of which work on the same principle of moving heat through evaporation and condensation.

Let’s take a closer look at how each of them and their applications….

Air-Source Heat Pumps (ASHP)

Air Source Heat Pumps are considered the most likely candidate for the majority of residential properties in the UK since their installation is less laborious and they do not require as much space to house. Being fully electrified they also align perfectly with the carbon-neutral goals. 

In terms of installation, they require a free external wall to house the unit, where the absorbed heat is fed into the property with a fan. 

How do air source heat pumps work? 

Air Source Heat Pumps, similar to a refrigerator, work on the principle of condensation and evaporation to extract heat from the outside air of your home. 

Watch Our Air Source Heat Pump UK Case Study in the video below: 

Essentially, this means that they reverse the normal state of thermal energy, moving it in the opposite direction of normal heat flow by extracting the heat from a cold location and releasing it to a warmer one. In a way, they make the indoors warmer by making the outside colder. 

There are two major types of air source heat pumps: air-to-water and air-to-air systems:

• Air-to-water systems
  Heat the water in your wet central heating system e.g. through your radiators, underfloor heating and hot water storage cylinders. 

• Air-to-air systems
  Heat the property with fans that can also provide cooling–like air conditioning, ideal for the warmer months of the year. For this reason, heat pumps are usually described as air conditioners that can work in reverse. 

• The elements fire and earth are excluded from the party.

Ground Source Heat Pumps (GSHP)

As their name suggests, ground source heat pumps extract air from the ground instead of the air. That means the fire is now the only excluded element from providing heat - ironically.  

Since the ground has an ambient temperature it is able to provide a much more consistent heat than the air, which can be relatively volatile. This is one of the major advantages of GSHP. 

However, in terms of installation, GSHPs are much more complex, requiring properties with large plots. Great news if you’ve got a castle. The installation process can also be incredibly disruptive, labour-intensive and expensive. 

More heat pump guides: 

• Do you need new radiators with a heat pump? 

• Heat pump grants. 

• Will a heat pump work in the cold? 

How do ground source heat pumps work? 

The ground surrounding the property must be trenched and a network of pipes containing refrigerant laid, this liquid then absorbs the heat which remains at a constant temperature of between 10°C and 15°C. It essentially turns your land into a giant underground refrigerator. 

Once heated, the refrigerant travels to a heat exchanger within the property where it’s used to generate heating water and hot water on demand. 

Hybrid Heat Pumps (HHP)

Hybrid heat pumps are seen as a more practical option in a seasonal climate like the UK, where the temperature can swing within a single day within a range of 20°C.

They are usually seen as a better option for older homes that are poorly insulated and/or have poor thermal efficiency. In these homes, it is increasingly likely that a fully electric heat pump would struggle to meet the heating demands consistently throughout the year. 

With regards to installation, a hybrid heat pump is simply the installation of both an air-source heat pump, which is an external wall-hung unit and a traditional gas combi boiler. 

How do hybrid heat pumps work? 

The hybrid heat pump system is composed of a heat pump that works in combination with a traditional gas boiler, the way Batman and Robin work together. 

The majority of heat pumps within these systems will operate at a temperature of 40 degrees C, which will provide sufficient heat for most of the year. The heat pump operates around 85% of the time and switches to the gas boiler when the external temperature plummets and the heat pump would struggle to meet the heating demands.

Hybrid heat pumps are not seen as a priority over full electrification systems, especially for properties off-grid where the required gas infrastructure would be far too expensive to install.

This is also true for modern, well-insulated properties, where regular heat pumps should provide adequate heat so that a hybrid option is not required. Poorly off-grid properties are clearly out of luck in these scenarios. 

Check out our review of the best heat pump brands of the year to find out which models are most reliable. 

Which type of heat pump is best for your home? 

This best type of heat pump for your home depends on a variety of factors, including the following: 

• Your budget 

• The size of your property 

• The plot your home resides on 

• The thermal efficiency or how well your home is insulated 

Ultimately a ground source heat pump is the best in terms of providing a consistent level of heat since the ambient temperature of the ground is consistent. However, it’s expensive and requires enough land for installation, but if you have the budget and the land (the two go well together, like wine and cheese), it may be preferable.

For most people in the UK, a standard air-source heat pump will be suitable, as long as you have a free external wall for installation.

However, if you have a property that is poorly insulated or for some other reason has poor thermal efficiency e.g. due to structural reasons, then a hybrid heat pump may be your best option.

Reside in the UK and wondering if a heat pump is right for you? Check out our complete analysis where we asked - are heat pumps worth it? 

Advantages of Heat Pumps 

Here are some of the major advantages of installing a heat pump in your home:

• Low carbon alternative 

  The appliance itself burns no fossil fuels and uses only electricity. Considering around 40% of electricity generation in the UK is produced via renewables it's certainly better for the environment than gas boilers.

  And with the government's legal obligation of reaching carbon neutrality by 2050, this is likely to improve further over time. The government’s legal obligation of today is your legal obligation of tomorrow. 

• Low-maintenance appliances & Safer

  Typically, a heat pump requires less maintenance, servicing and repairs than a traditional gas boiler. In comparison, there are also rarely any safety concerns and since they don’t burn gas, there are fewer risks associated with their use (although unburned gas is even more dangerous). 

• Superior efficiency 

  The average heat pump has an efficacy rating of 300%, while gas boilers have an average efficiency rating of around 90%.

• Provides cooling and heating

  A heat pump can work in reverse meaning that it can remove heat from your home when it’s hot, much like an air conditioning unit.

Disadvantages of Heat Pumps 

As with most things, it’s not all good and there are some disadvantages when it comes to heat pumps: 

• Significant upfront costs

  If you are installing a ground source heat pump or a hybrid i.e. an air source heat pump and a gas boiler, then the upfront installation costs can be extremely high.

  In fact, the Committee on Climate Change (CCC) has estimated that it would cost an average of £26,000 to switch each UK home to a low-carbon heating system. That’s pocket money very few people find in their couch cushions. 

• Running costs can be very high

  If used incorrectly or in a home with extremely poor thermal efficiency, the running costs can be extremely high, especially in comparison to gas. In any case, the cost of electricity is currently much higher than gas, meaning it has an extremely high running economy, for example, electricity costs 3-16p per kWh compared to gas’ 3-4 per kWh.

• Often requires other upgrades 

Heat pumps often need to be installed with a heat pump-compatible hot water storage tank and in some cases may require other upgrades like new, larger radiators and home insulation. And none of these upgrades are actually fun. These additions can drive up the costs even further. 

Heat Pump Frequently Asked Questions (FAQ) 

#1. How do Heat Pumps work? 

Just like a refrigerator, an air source heat pump utilizes a liquid called a refrigerant (commonly R410, R290, R744 or R32) which controls the movement of heat through evaporation and condensation. This refrigerant is contained within a closed circuit. 

Here’s a step-by-step example of how the heat pump operates: 

• If the external temperature of your home is 8°C, an electrical fan will blow air into your heat pump and it will pass over an evaporator heat exchanger containing the refrigerant (currently very cold and in a liquid state). 

• Next, the fluid will pass down a pipe to a compressor, where it will be heated further via compression. For example, the refrigerant may reach 80°C, leaving the compressor transformed from a liquid into a hot gas. 

• Once heated, the gas will pass into a condenser heat exchanger, designed to transfer the heat from the gas to your water pipes in your central heating system. 

• As the hot refrigerant gas travels through your heat exchanger heating the water, it will have cooled and so travels back to an expansion vessel. Here, it rapidly expands and returns back to a cold, liquid state. 

• The liquid refrigerant returns back to the first heat exchanger ready for another cycle of absorbing air from the outside and back to the compressor. 

• Your house feels nice and warm (but it won’t hurt to wear a jumper).

#2. Is a heat pump suitable for my home? 

Many homes in the UK could work well with a heat pump, however, lots of properties have a very poor thermal efficiency i.e. they lose a lot of heat and so key home improvements would be appropriate. This includes installing roof and wall insulation, double-glazed windows and draught-proofing your property. And closing that door your kids keep leaving open for longer than necessary. 

If you live in a home with typical thermal efficiency, during the winter months you will probably need to run your heat pump for longer and at a higher temperature. 

In some cases, it’s possible that heat will be lost from your home faster than the heat pump can warm it up. For example, a 3 bedroom house should have heat losses of 6kW, but some poorly insulated properties have heat losses of up to 15kW. In these situations, improving the thermal efficiency of your home is likely going to be recommended. 

#3. Will I need to replace my radiators? 

Potentially, yes.

Your radiator's job is to radiate the heat into your home and the larger the radiator is, the lower the temperatures it can cope with while still keeping your house warm. 

If you have an average-sized, well-insulated room, then a heat pump should work well with a standard-size radiator. However, if you have a larger poorly insulated room, you may need to upgrade your radiators to larger, or even triple panel radiators. If you need quadruple radiators, it probably means you’re missing a wall. 

#4. Is financial support available for heat pumps? 

The Green Homes Grant ended in March 2021 but at the time awarded vouchers towards the cost of green home improvements which included the installation of heat pumps but not green boilers, unfortunately. 

Currently, you may be able to apply for the Renewable Heat Incentive (RHI). It’s the source of the heat that’s renewable, not the heat itself. 

The Domestic Renewable Heat Incentive (Domestic RHI) is a government financial incentive to promote the use of renewable heat. Households both on and off the grid can apply for the scheme.

You’ll receive RHI cash payments quarterly over seven years. The amount you receive will depend on a number of factors.

Since the green reform of domestic heating is a moving picture, updates are frequent and so it’s quite possible new incentives and support will be available in the future. 

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Heat happy.