The Ultimate Guide to Choosing Air Source Heating And Cooling

Check now

Understanding air source heat pumps for your home

When upgrading any aspect of your home heating, it can only be a good thing to gain a full and thorough understanding of every single option available. And whilst you probably know about the basic merits of radiators and heated towel rails, air source heat pumps are one vice that probably aren&#;t so universally recognised or appreciated.

We&#;re looking to change that, so we&#;ve put together a guide covering how air source heat pumps work, what are the upfront costs of an air source heat pump as well as running bills, and how they can impact on the overall operations of your home heating.

Can they work alongside radiators? Act alone as an energy efficient heat source indoors or outdoors? Or be teamed with your existing central heating system to deliver sufficient hot water and a generally impressive heat output?

What are the pros and cons of air source heat pumps?

We&#;ll answer all these questions and more in this, our Ultimate Guide to Air Source Heat Pumps.

What is an air source heat pump?

Generally, the vast majority of home heating systems generate heat via the burning of fuel, or conversion of electricity. Air source heat pumps differentiate greatly, as they don&#;t actually generate heat.

Instead, an air source heat pump will transfer heat from the outdoors to inside a building or the other way around.

It does so by making use of a refrigerant system that features a condenser and compressor to absorb heat in one area and release it in another space.

For domestic properties, an air source heat pump will soak up heat from the air outside and release it within the home via hot water-filled radiators, underfloor heating, hot air or as a hot water supply.

Essentially, air source heat pumps can operate in the same manner that a traditional gas boiler does. They can keep your home nice and cool in the summer, toasty warm in the colder winter months, and provide hot water up to optimal temperatures of 80°C.

Furthermore, they perform in an economically friendly manner, as they don&#;t feed off fossil fuels and thus don&#;t give off any carbon emissions.

So, how do air source heat pumps operate?

How do air source heat pumps work?

A good way to think about the way air source heat pumps actually work, is to imagine them performing in the opposite way to a fridge, thus heating your home as opposed to cooling it.

The air from outside travels over a conglomeration of tubes containing refrigerant fluid. This heats the refrigerant up, transforming it from a liquid into a gas.

At this point, the gas journeys through a compressor to enhance the pressure and ramp up the heat. The compression process harbours similarities to topping up the air pressure in car tyres, with the air hose heating up simultaneously.

From there, the warm, compressed gases make their way into a heat exchanger, shrouded by water or cool air. The refrigerant will then shift its heat to the cool air or water, all the while warming it up. This energy is then distributed around the indoor space to deliver a heat output.

Whilst your home is warming up, condensation leads the refrigerant to return to a cool liquidated state before the cycle begins again.

What types of air source heat pumps are there?

There are two main types of air source heat pumps, broadly defined as air-to-heat and air-to-water models.

We&#;ve already touched on how the air-to-heat air source heat pumps operate &#; largely like a refrigerator does in reverse.

In the case of air-to-water heat pumps, the process is slightly different. Heat is gathered from the outside air before being fed into your wet central heating system.

Considering that the heat distributed is cooler than that typically provided by a conventional boiler, you might find it is necessary to fit underfloor heating, bigger radiators, or more designer radiators to make up the heat output deficit.

One of the most attractive aspects of air-to-water heat pumps for potential buyers though, is that they qualify under the government-led Renewable Heat Incentive (RHI). This could offset the cost of purchasing multiple supporting heating components, for instance.

This scheme essentially contributes cash towards the running costs of renewable heating in homes.

As such, air-to-water heat pumps are particularly popular options for new-build properties. They can also prevent large-scale potential disruption to your home&#;s aesthetic and massive future outlays by including the air source heat pump within the initial building specifications.

The retrofitting of underfloor heating can be an extremely timely, invasive and expensive practice, for instance, as explained in our Ultimate Guide to Underfloor Heating.

Meanwhile, there is one more type of air source heat pump to touch on, despite its design and way of working rendering it far less conducive to efficient home heating efforts than its counterparts.

Air-to-air heat pumps simply take heat from the outside air and use fans to spread it throughout your home. The big drawback with these systems, and a deal breaker for most, is their inability to produce hot water.

Do air source heat pumps need electricity to run?

All types of air source heat pumps need electricity to run. However, the way they operate ensures they will generate more heat than the amount of electrical energy they consume, effectively making them far more energy efficient than traditional electric home heating means.

Just how much more efficiently they perform will relate specifically to which make and model you opt for, and you can gain a deeper insight in our blog on The Ins And Outs Of Modern Electric Heating.

To measure the efficiency of an air source heat pump, or put more simply, how much heat energy it delivers per kW of electricity, the pump itself will usually be referred to as a SCOP, which is an acronym for Seasonal Coefficient of Performance.

Typically, this will be displayed as a simple number that refers to the level of heat energy produced in kilowatts per every 1kW of electricity utilised.

As an example, should an air source heat pump boast a SCOP of 3.2, it indicates that 3.2kW of heat will be emitted per every 1 kW of electricity it saps.

What is the difference between air source heat pumps and ground source heat pumps?

There are several standout differences between air source heat pumps and ground source heat pumps, and the main one sticks out like the thumb you clobbered with a hammer whilst putting together one of our radiator covers.

That is, of course, the way they source their heat. As each moniker would suggest, air source heat pumps take heat from the air, whilst ground source versions will make like Paul Weller, and go underground to consume inherent heat.

Ground source heat pumps would tend to deliver a slightly more efficient performance than their air source counterparts as well. Making use of the SCOP measurement method aforementioned, air source heat pumps will usually garner a SCOP rating in the 3.4 region, whilst ground source heat pumps will generally be in the 4.2 range.

With regards to installation, it&#;s more of a rigmarole to fit ground source heat pumps, with significant invasive groundwork required to provide a suitable foundation. Either a large surface area will need to be dug up, or a deep borehole created to store the system pipes underground. Unless you&#;re qualified to carry out this sort of work yourself, you&#;ll experience much higher initial installation costs for ground source heat pumps, as no such efforts are involved in fitting air source options.

However, the Renewable Heat Incentive Scheme does offer bigger rewards for ground source models, so you can expect to see a better return on your investment for selecting that type. Whilst the figures are subject to change and it can be a volatile barometer, the use of ground source heat pumps would allow the owner to claim 21.16p per kW of energy used, according to the latest published statistics from the Ground Source Heat Pump Association. By contrast, air source heat pumps fetch RHI payments of 10.85p per kW at this time, but as stated, these values are prone to fluctuation. Our UK Heat Pump Grants blog features a more detailed account of government incentives as it pertains to various heat pumps, while this also more information in this air source heat pump guide from the Energy Saving Trust.

How much do air source heat pumps cost?

Sensibly, pricing will be at the very forefront of concerns for most would-be buyers of air source heat pumps. And rightly so, considering they represent a very significant investment.

Generally, a good quality air source heat pump will cost somewhere in the vicinity of £7,000. But when factoring in installation costs too, you probably won&#;t be getting much change out of £10,500.

But don&#;t forget to consider the RHI payments you&#;d be eligible for once the system is up and running, and also think to compare the cost of this type of heating system with other renewable energy vices.

Plus, the fact that from April , the government plans to provide homeowners in the UK and Wales with £5,000 subsidies to swap gas boilers for air source heat pumps (more on this later).

A working, fully installed ground source heat pump can cost between £14,000 and £20,000, whilst biomass boilers tend to start at £15k and have a similar price ceiling to ground source heat pumps. And whilst the most commonplace of heating systems in gas combi boilers are also comfortably the cheapest to buy at between £1,500 and £3,500, they&#;ll cost more to run year after year and time after time.

If you&#;re lost, you can look and you will find that once fitted, air source heat pumps are likely to cost around £750 per year to run, which is comfortably cheaper than a standard gas combi boiler would (£900 &#; £1,000).

Add in the money you would receive under the government&#;s Renewable Heating Incentive scheme, and the impact an air source heat pump can have on your heating bills over time becomes more appealing still.

Government grants for air source heat pumps

In addition to the Renewable Heat Incentive payments already discussed, new plans unveiled in October suggest that new government grants will be available to incentivise the installation of air source heat pumps for homeowners.

Property owners in England and Wales will be entitled to receive £7,500 subsidies from April and beyond to help them replace old gas boilers with low-carbon heat pumps.

The move will form an integral part of a £3.9bn government plot to reduce carbon emissions in the heating of homes and commercial buildings.

Basically, it will act as a leg up for homeowners to swap their gas boilers for air source heat pumps, in the hope that no new boilers will be sold after .

The overall aim is to make homes and business properties more energy efficient, and whilst the proposition has drawn initial criticism for lacking ambition, it is certainly welcome news for those already considering a switch to an air source heat pump.

Even if, as experts suggest, the proposal will struggle in its aim of drawing 600,000 air source heat pump installations across the UK by , it is certain to attract more homes and businesses to considering swapping gas boilers for low-carbon heat pumps.

The advantages and disadvantages of air source heat pumps

At this point of the article, you&#;ve probably ascertained for yourself what some of the main plus points and drawbacks are concerning the purchase and installation of air source heat pumps.

Even so, we&#;ve not covered everything just yet, and it&#;s always handy to have all the most important pros and cons compiled into a neat and tidy shortlist.

Below are the main benefits and drawbacks of air source heat pumps.

Advantages

• Easy installation &#; In comparison with other economically friendly heating solutions, air source heat pumps incorporate by far the easiest installation process. As a result, they are cheaper to fit than other green heating options as well.
• Economically friendly &#; An air source heat pump operates in a far more economically friendly manner than a traditional gas boiler. As such, your home heating will emit far less CO2 to the earth&#;s atmosphere.
• Renewable Heating Incentive eligibility &#; You&#;ll qualify to receive RHI payments under the government-led scheme if you choose to fit an air source heat pump. Therefore, you can be confident of garnering a significant return on your investment over time.
• Cheaper to run &#; In addition to enabling you to earn some kickback from the Renewable Heating Incentive program, air source heat pumps will also prove cheaper to run than a traditional gas boiler would. So you can enjoy lower energy bills as well as regular RHI sweeteners.

Disadvantages

• Initial cost &#; The typical main concern for would-be investors in air source heat pumps is understandably the initial cost. Although they are cheaper to buy and install than alternative renewable heating solutions, air source heat pumps still cost a pretty penny to secure and set up. Considerably more so than the more popular conventional gas boilers do.
• Heat output &#; Generally speaking, air source heat pumps do not always provide as high a heat output as you might require to sufficiently heat a home. You may require additional or larger radiators to deliver an adequate level of warmth, whilst some air source heating systems explicitly state that they will perform better alongside an underfloor heating system. (There&#;s no fancy talking version, but their manual will indicate as much.)
• Noise &#; Significant noise can emanate from air source pump condensers, which will also emit cold air. The persistent sound could be irritating if you are nearby to the unit situated on the outside.
• Electric operation &#; Air source heat pumps require electricity to operate successfully, so they can&#;t be described as an absolutely zero-carbon venture. That is, of course, unless you generate electricity for your home via another renewable energy source such as a wind turbine or solar panels.

Is there a cheaper air source heat pump alternative?

Given that so many see the initial purchase price as a major deterrent to fitting an air source heat pump, plenty of people will be interested in seeking a cheaper renewable heating alternative.

Of course, over the course of its lifespan, an air source heating system will in essence pay for itself and work out a lot less expensive to run than a traditional gas boiler. But if you aren&#;t in a position to invest so heavily up front, an air source heat pump investment will unfortunately be a non-starter.

So, are there any reasonably priced alternatives that work in a similar way?

Sorry to be the bearer of bad news, but in all honesty, air source heat pumps represent the cheapest and most economically friendly domestic heating option available.

If they are beyond your budget from an initial outlay perspective, the likeliest next best proposition is a contemporary, energy-efficient gas boiler.

These won&#;t come spectacularly cheap either, but at a much more generally affordable cost (£1,500 &#; £3,500) than an air source heat pump would. And they&#;ll be worth the extra cash as well &#; the modern models will perform far more energy efficiently than an old gas boiler would, leading to reduced heating bills over many years moving forwards.

Get in touch with BestHeating

Hopefully, by now you&#;ll have a solid understanding of how air source heat pumps work, and the lasting impact they can have on your home heating bills and operations, as well as their positive environmental impact.

Forlssman Product Page

If you would like to know more about air source heat pumps, or any other renewable home heating options, please don&#;t hesitate to get in touch with us. You can leave your thoughts in the comments section below, or contact us via Instagram, Facebook or Twitter.

With a background in sports journalism, John counts content writing amongst his key passions. He&#;s always peppering our Advice Centre feed with reasoned and researched home heating tips, and providing expert solutions to the questions you want answering. Fine football and music connoisseur. In his own head, at least.

Air source heat pumps are soon to be mandatory in all new build homes, with the government's Future Homes Standard exploring two options, both of which will see the low-carbon heating option required to be installed by law.

Existing homes will also be increasingly likely to adopt heat pumps with the government looking to roll out a gas and oil boiler ban by and offering homeowners up to £7,500 through its Boiler Upgrade Scheme. However, as appealing as that might sound, it is not always a straightforward swap.

Installing an air source heat pump will ideally require improvements to the fabric of a home to operate efficiently. But once this is achieved, air source heat pumps are hard to beat when it comes to producing renewable heating.

Our heating expert David Hilton takes an honest look at all the pros and cons of air source heat pumps so you can assess whether one makes sense in your project.

Air source heat pumps

An air source heat pump is a low-carbon heating source. It uses a refrigeration cycle to move heat from the air outside and transfers it as useable heat in your home.

Air source heat pumps, like boilers, are a heat source, but they deliver lower temperatures than a boiler. As such, they ideally need to be carefully designed into well-insulated, airtight homes to ensure optimum efficiency.

However, heat pumps work very differently to boilers in that they don't create heat &#; instead they move heat from one place to another through the vapour compression cycle (or refrigeration process) to make it useable.

There are two main types of air source heat pump:

• Air to water heat pumps are used in wet central heating systems to heat radiators, underfloor heating and sometimes to generate hot water.
• Air to air heat pumps are perhaps better known as air conditioning, and heat the air directly. This will include some level of air movement and noise as you'd expect from an air conditioning unit.

This article will focus on air to water heat pumps. These work by heat being absorbed into a fluid from the air, which causes it to &#;boil&#; and become a gas. The gas is then compressed, raising its temperature. The higher temperature is then transferred into the heating system (i.e. the radiators or underfloor heating).

The efficiency of a heat pump, or rather the measure of the heat energy output per kW of electricity, is stated as the COP (Coefficient of Performance) or SCOP (Seasonal Coefficient of Performance). The SCOP is the average COP over a defined period of time, such as a year. For example, a SCOP of 3.2 means that for every 1kW of electricity, 3.2kW of heat is generated.

It is also worth noting that air source heat pumps need electricity to power them. This can be from the grid or from renewable energy sources such as solar panels (ideally with solar battery storage), assuming it can generate the required amount of power.

Pros of air source heat pumps

It is essential to design and specify the system correctly. When it comes to knowing is my home suitable for a heat pump, ideally the insulation, airtightness and emitters (typically underfloor heating or carefully sized radiators) of the property should be optimised to allow you to get the most out of your air source heat pump.

There are many benefits to installing an air source heat pump, including:

• Unlike a gas boiler, an air source heat pump does not produce carbon when operating. While they do use electricity, ASHPs can be combined with solar PV panels or a renewable/green energy tariff for clean electricity.
• In the right context, air source heat pumps have comparatively low running costs, especially when compared with off-grid fuels such as propane, oil or direct electric heating. The cost of installing an air source heat pump will depend on the complexity of the install, alongside factors such as the distance from the heat pump unit, as well as whether or not the homeowner can take advantage of grants such as the Boiler Upgrade Scheme.
• The outdoor unit takes up less space when compared to an above-ground oil or LPG tank.
• Air source heat pumps partner well with underfloor heating.
• There are certain grants available to offset the costs of installing an air source heat pump, such as the Boiler Upgrade Scheme.
• Some models can also be used for cooling a home, but you will need to weigh up heat pumps vs air conditioning before opting for this solution.

Cons of air source heat pumps

While there are many benefits, there are also some cons too, including:

• They are not a &#;one-size-fits-all&#; solution and may not be suitable for every home in the same way as gas boilers are. They're ideally paired with well-insulated, airtight homes.
• Installing an air source heat pump in an existing home is more complex and replacing a gas boiler will inevitably be much more expensive than a like-for-like replacement.
• Electricity is still needed to power an air source heat pump, so they are not entirely 'renewable' unless paired with PV panels or a renewable energy tariff.
• Electricity prices are currently high. Campaigners are asking the government to move environmental levies off electricity bills, with the focus on air source heat pumps, to ensure that it's always cheaper to run a heat pump than a gas boiler.
• The bigger the difference between the outside air and the target temperature (either the indoor room temperature or domestic hot water), the lower the efficiency.
• A separate solution may be required for providing hot water for the home.
• If you want to know are air source heat pumps noisy, some may reach 40 to 60 decibels, but this depends on the manufacturer and installation, according to Quiet Mark, which certifies the quietest heat pumps.

Air source heat pumps are often best suited to new build projects due to working more efficiently in well insulated homes

(Image credit: Daikin)

Using an ASHP for heating and hot water

One of the key decisions to make when buying an air source heat pump is whether it will provide space heating or domestic hot water &#; or both.

The &#;flow temperature&#; (the temperature of the water in the heating system) is lower in a heat pump than it is in a boiler. This means:

• Space heating will usually require a flow temperature of around 35°C to 45°C for underfloor heating or low-temperature radiators.
• Domestic hot water will, however, require a minimum flow temperature of 55°C.

On new homes that meet recent and current Building Regulations, most air source heat pumps can do both, but this is not always the case.

Having two heat pumps as a solution

One solution is to use two heat pumps: one that is optimised for the space heating and another for domestic hot water.

The advantages of using the two heat pumps is that each unit is optimised for the required flow temperature and there is no priority system that causes the space heating circuit to &#;cool&#; while the domestic hot water is being reheated.

The domestic hot water heat pump typically uses a different refrigerant that can produce higher flow temperatures but also requires a higher source temperature (10°C) to be efficient.

It tends to be lot smaller than a space heating heat pump and is usually built into the hot water cylinder. It draws its air from the room it is in, or the kitchen or bathroom (or all of them) or from the exhaust waste heat of a ducted mechanical ventilation system &#; and is known as an &#;exhaust air heat pump&#; or a &#;micro heat pump&#;.

It is crucial that this system is designed properly so as to not over ventilate the property and only uses heat from the air that would normally have been exhausted to atmosphere.

Having a high temperature heat pump

A further option is a high temperature heat pump. There are different variants available, but these could offer temperatures of 60-80°C.

In order to achieve higher temperatures, some manufacturers have built the two different refrigerant systems into one heat pump in a &#;cascade&#; system that can create flow temperatures of up to 80°C.

These systems are designed for hot water and should not really be used as a high temperature boiler replacement unless the lower efficiency has been carefully calculated to ensure that it is the best option for the property. In other words, they're best suited to well-insulated, airtight homes.

Heating is rarely used in this contemporary self build in Surrey &#; the house, which has an EPC A rating, is heated with an air source heat pump, installed by TerraTherma.

(Image credit: Jeremy Phillips)

Assessing whether to install an ASHP

An air source heat pump for a new home

The efficiency of an air source heat pump is dependent on a number of factors, including the fabric of your home. In a new build, especially one that has been built with fabric first principles at the forefront, equipping your home with an air source heat pump is definitely worth considering. Not only do they offer low carbon heating for your home, they're also reliable and last much longer than a gas boiler.

Air source heat pumps do not tend to go wrong too often either, and a good quality air source heat pump could last up to 20 years. Pair that with the potential to regain some of the initial expense through the Boiler Upgrade Scheme, and it's a worthwhile investment in the future of your home.

An air source heat pump for an existing home

Did you know?

Hybrid heat pumps are also available, which combine an air source heat pump and gas boiler together in one box, designed to work in partnership and get the best from each heating system.

Should I swap my boiler for an air source heat pump? is a popular question at present. It's not as simple as it sounds to switch, and deciding to retrofit an air source heat pump in an existing home will mean certain changes will need to be made.

A boiler works at a high flow temperature of around 70°C, but an air source heat pump operates at a lower temperature &#; around 35°C to 45°C for the radiator system and around 55°C for hot water.

Unless your home's current radiators are over-specified, it's likely you'll need to replace radiators with new ones that have a higher output, alongside room by room controls and a heat pump-compatible hot water storage.

The lower temperatures will also mean that an air source heat pump is ideally compatible with homes that have high levels of insulation and airtightness.

The levels of insulation and airtightness are often not optimised in older properties. This would cause the heat pump to operate at increased flow temperatures, resulting in lower efficiency and higher running costs. This will mean added cost in remedying these immediate fabric issues before installing an air source heat pump.

"The problem homebuilders and government bodies are facing is the way we have historically built our homes. The s era of homebuilding ignored fabric heat loss as gas was cheap, which led to the installation of gas central heating," says Keith Bastian, CEO of renewable home heating provider Fischer Future Heat.

"This building approach has put us an a big disadvantage to install heat pumps," continues Keith. "A house that is poorly insulated will require a larger heat pump to make up for heat loss, and this could cost more money to install and to run."

Finally, when weighing up a heat pump vs a gas boiler in an existing home, an air source heat pump may actually cost more to run (though is much more sustainable), so when it comes to retrofitting a heat pump, it's often more attractive when replacing a more expensive heating system such as electric heating.

Keith Bastian

CEO

Keith has more than 25 years of experience in the heating industry, bringing German manufactured electric heating to the UK in through his company Fischer Future Heat. The company has now installed over 250,000 heaters in UK homes.

(Image credit: Quiet Mark / Grant)

Checklist for whether to install an ASHP

There are some key criteria your home will need to meet to make installing an air source heat pump viable, including:

1. Do you have enough space for one to be installed? You'll need to have space for a unit to be attached to a wall or fitted on the ground, with space around it to ensure a good airflow. For an air source heat pump to be installed under Permitted Development, it also needs to be located at least one metre from the boundary of the house. The internal unit for an air source heat pump is generally smaller than a gas boiler. However, you will need space for a hot water cylinder, if you do not have one already, and controls.

2. What heating system will you use? The big question: do air source heat pumps work with radiators? For space heating, air source heat pumps work best with underfloor heating, but low-flow temperature radiators, such as oversized radiators, multi-finned aluminium radiators or fan convectors, will work as well. In existing homes, this might require you to upgrade the radiators you already have.

3. How well insulated is your home? Air source heat pumps work more efficiently when producing heat at a lower temperature, so a home that requires less space heating because it is better insulated is key to getting the most from this technology.

4. What system are you replacing? The initial expenditure of an air source heat pump is high, even with a government-funded grant helping claw back some of the outlay. Air source heat pumps are much more cost-effective to install in a new home, as the pipework and emitters will be designed around them from the outset. In an existing home, the installation may necessitate work to the existing heating system.

A 4kW Earth Save air source heat pump was installed in this energy-efficient self build home on the Isle of Man. Air source heat pumps need to be positioned at least one metre away from the boundary to fall under Permitted Development.

(Image credit: Jeremy Phillips)

FAQs

How long does it take to install an ASHP?

Air source heat pump installation is a relatively low-disruption process which could take as little as a single day to undertake.

A solid base for the air source heat pump should be constructed and, when retrofitting, all alterations to the fabric of the house and radiator systems should be completed before the installation date.

An air source heat pump should be installed and commissioned by an accredited Microgeneration Certification scheme (MCS) installer. An incorrectly commissioned air source heat pump may use a lot more electricity.

(Image credit: Daikin)

Do air source heat pumps work in winter?

Do air source heat pumps work in cold weather? An air source heat pump gets its energy from the surrounding air, so as the ambient air temperature drops, so does the efficiency. It is therefore key to understand the heat load of the property and the performance characteristics of the heat pump.

When it gets closer to zero degrees outside, the air source heat pump will also need to perform a defrost cycle more often and this will also lower the efficiency.

However, while the efficiency may drop, that doesn't mean that air source heat pumps don't work in cold weather. It's been found that they can extract heat from the air in temperatures as low as -20°C, and are used in cold climates around the world.

For more information on living with an air source heat pump, read my Mitsubishi Ecodan 11.2kw heat pump review and find out how to maintain a heat pump. Or, if you're looking for an alternative to a gas boiler, but don't think an air source heat pump is right for your home, there are many other systems you could investigate, including ground source heat pumps, a biomass boiler, solar thermal and hydrogen heating.

If you are looking for more details, kindly visit Air Source Heating And Cooling.