Air Source Heat Pumps (ASHP), are a relatively modern energy–efficient heat source that uses heat from the sun stored within the atmosphere. The air source heating technology works similarly to an average refrigerator but in reverse. A fridge takes heat away from the interior of the fridge and dissipates it to the environment through a heat exchanger. Similarly, a heat source pump takes heat from the environment, ‘amplifies’ the energy using a compressor and transfers the heat to your central heating system.
The cost of an air source heat pump installation lies between about £8000 and £17000, whereas the running costs will be a small fraction of your present heating bill. However, the actual savings in heating varies depending on the size of your house, how well insulated it is, the type of fuel you previously used, and the age of your central heating boiler.
How Much Does an Air Source Heat Pump Cost?
As an ASHP harvests the solar energy stored in the atmosphere, the running costs will be a lot less than standard central heating boilers.
Air Source Heat Pump Prices
Sizing an ASHP is never easy. Not only must you take into account the floor area and required indoor temperature, but also you must consider the insulation, average outside temperatures and many other factors. To get this information, you need a comprehensive energy survey. However, for our purposes, we can estimate approximate prices. Furthermore, you must remember that as technology continually improves, and the heating method becomes more popular, air source heat pump prices reduce.
|Property type||Recommended output (kW)||ASHP Purchase & Installation costs|
|Detached House||9||£8000 to £16000|
|Semi-detached/terrace house||6||£7000 to £10000|
|Flat||5||£6000 to £8000|
Installation Cost Factors
The total costs of a heat pump chosen specifically for your circumstances depend on factors such as the:
- Size of your home. Whether your home is well insulated.
- The pump size.
- The pump branding.
- Pump’s performance and efficiency.
- What room temperature you want to achieve.
You’ve probably already noticed that heat pump prices vary over a wide range. The only sure way to find out an accurate cost is to have a survey done by your installer. It’s up to the installation company how much they charge for this. But, usually, an initial survey costs nothing and is absorbed by the installation costs.
You also need to make sure you have a suitable central heating system in place that the ASHP can use efficiently. If you previously had electrical storage heaters, you’ll have to install new pipework and radiators. But, if you have an older central heating system, consider upgrading to larger radiators or underfloor heating to make efficient use of the lower ASHP temperatures.
For these reasons, it’s often very expensive to retrofit an existing house unless you’re doing major renovations. Often, it’s far cheaper to install air heat pumps into new build houses, and in fact, that’s what developers now do.
How do they work
Although it might seem unlikely that a domestic heat pump can extract usable heat from the outside atmosphere, it’s actually very simple to do. An ASHP can extract heat from air with a temperature as low as -20°C. So, you can see that you’ll get useful heat from even the coldest days of a British winter. The heat pump comprises an impellor, an evaporator and condenser, a refrigeration circuit and a compressor wrapped in sound and heat insulation. The energy transfer uses a small amount of electricity to operate the pump but doesn’t use it to provide heat. You, therefore, end up heating your home for less money.
Air Source Heat Pumps Benefits
Air source central heating technology has many advantages, such as being:
Easy to install
Compared to ground source heat pumps which need excavation, they are very easy to install.
ASHP systems need less maintenance compared to gas and oil–fuelled boilers.
You aren’t bringing a highly flammable and explosive fuel into your home. So, there’s less chance of accidents. In fact, the level of danger is equivalent to a fridge being kept in your garage.
No fuel storage
If you live in an area that doesn’t have mains gas piped to your home, the only other alternative was to store bottled gas or a tank of heating oil on your premises. An ASHP doesn’t need fuel to produce heat, it harvests the energy from the surrounding air.
The electricity needed to operate an air source heat pump increases its carbon footprint marginally. An ASHP generates much less carbon dioxide than traditional fossil fuel heating systems. In fact, if you want to reduce your carbon footprint even further, you can generate your own electricity using solar or wind technology.
Heating and cooling
Some models not only heat your house in winter, but they can also cool your home in summer. After all, its the same technology, but in reverse.
Compared to traditional central heating systems they have a much longer lifespan. Previously, their lifespan used to be about 15 years. However, several technological improvements have increased this to about 25 years. Remember that the lifespan of any machine depends on regular maintenance.
Air Source Heat Pumps Disadvantages
We’ve just seen that there are many advantages when using ASHPs. However, they’re not perfect. In fact, they have a few disadvantages too.
The condensing unit needs to be sited outdoors and takes up room in your garden. Admittedly, they aren’t large pieces of equipment, about the same size as a domestic air conditioning unit. However, if you have a small garden, like many new builds, it will take up a considerable percentage of your recreational space.
The condenser can be very noisy. Even more so, if you live in a quiet area. Although most heat pumps have good sound insulation installed, it’s never 100%.
Usually, machines give off heat which warms the immediate environment. On the other hand, heat pumps give off cold air.
Although the electricity used to power the heat pump is much less than would be used to produce the same amount of heat, it still needs energy to run the machines. Ideally, you could generate enough power using solar or wind technology. But, most of us will use power from the National Grid.
Backup in winter
Depending on the type of heat pump you have and where you live, you might need to use another heating method to keep temperatures at a comfortable level during a severe winter. However, winters in the UK are usually never too cold.
Types of Air Source Heat Pumps
There are two types of ASHP that work in different ways.
Air to Air heat pumps
This system warms the air inside the house, which circulates the rooms using ducting. The method, however, doesn’t heat water so you need another way to provide hot water to the house.
Air to water heat pumps
This system distributes heat around the house using your existing ‘wet’ central heating system. You, therefore, have energy for the central heating system and hot water. Heat pumps work very efficiently at lower temperatures than a standard boiler using traditional fuels. Therefore, it’s better to use underfloor heating and large radiators in your central heating system as these work better at low temperatures too.
How Much Can You Save?
Using air source heat pumps allow you to save money on your energy bills. But, there are certain criteria that you must consider, and these will govern how much money you can save.
You can measure the efficiency of an ASHP by looking at its Seasonal Coefficient of Performance (SCOP or just COP). This coefficient is the ratio between heat energy generated to the energy needed to operate the ASHP. For example, A typical value for COP could be 3.0 at an outside temperature of 7°C. This means, for every kW needed to operate the fans, pump and compressor, the equipment produces 3.0kW of heat energy. Alternatively, you can say that the air source heat pump efficiency is 300% at this temperature. Or, it gives out three times the energy it uses! This sounds impossible, right? Actually, no-one broke the laws of physics. Because the energy is in the surrounding environment and an ASHP uses a small amount of electricity to harvest it.
Although air-source heat pumps can operate at temperatures as low as -20°C, they work at lower efficiencies when the outside temperature is less than 0°C. Furthermore, any benefit from using an ASHP can be negated if your house isn’t insulated to the current levels specified by the UK Building Regulations. Fortunately, the average UK winter temperature lies between 0°C and 7°C, so an ASHP works well at these temperatures.
Air Source Heat Pump Grants
You might have electric storage heaters or an old fossil-fuelled boiler. If so, and feel you’d like to take advantage of an air source heat pump, but don’t think you can afford one right now, the UK Government set up The Renewable Heat Incentive (RHI). This provides a grant to help domestic and non-domestic consumers switch onto renewable energy sources. And so, reduce the country’s carbon emissions. Both the UK Government and Ofgem websites give more information and they’re definitely a worthwhile read.
The scheme gives those who join and stick to the rules, a quarterly payment for 7 years for the renewable energy their system produces. The amount you receive usually covers the cost of installation so in the long term you won‘t be ‘out of pocket’. One of the requirements states that the equipment and installer must be registered by the Microgeneration Certification Scheme (MCS). This requirement ensures the equipment and installation procedures meet with an approved level of quality and comply with the industry standards approved by the UK Government. The RHI doesn’t just cover air source heat pumps, so if you finally decide to use another method of renewable energy generation, you might still be eligible. Do some research and find out a bit more about the grant scheme, as the terms and conditions change now and again.
Domestic RHI Scheme Earnings
The amount of RHI scheme earnings you receive will depend on various factors:
- Do you live in Scotland or England and Wales?
- Do you have a recent domestic Energy Performance Certificate?
- What type of house do you live in?
- How old is your property?
- How many bedrooms do you have?
- What type of roof and depth of loft insulation?
- What type of walls do you have and are they insulated?
- Which method of heating do you currently use?
You can use the official UK Government Domestic RHI calculator to estimate how much you should receive by changing from various conventional heating methods to one of the renewable heating sources. Remember that the calculator only gives an approximation, so the actual amount of government funding for an air source heat pump might vary.
Let’s assume we have a typical 3 bedroom terraced house with a floor area of about 85m2, with loft insulation and cavity wall insulation complying with the UK Building Regulations. However, we have an old and out-of-date energy performance certificate. Using the online calculator we get the following results:
|Previous heating method||RHI income (per annum) for ASHP|
|Gas boiler (pre–2005)||£760|
|Heating oil (pre–2005)||£760|
|Electric storage heaters||£850|
|Solid fuel heating||£790|
Don’t worry if you live in a different type of house with another type of heating method. You can still work out how much you’ll receive. Simply use the online calculator.
Air Source Heat Pump Running Costs
ASHP running costs depend on 3 factors. First, the heat pump’s efficiency. Next, how much heat you need for your home. And finally, the temperature of the heat source (outside air). Additionally, from these factors, you can derive the Coefficient of Performance (COP). This value will give you an idea of the amount of energy you use and generate at a particular temperature. From this, you can calculate your running costs.
Let’s look at a specific example, shall we?
Assume we have an air source heat pump, that for every kW electricity used, will generate 3kW of heat (therefore, its COP is 3.0).
We can assume that an average electric bill for a 3 bedroom house in the UK shows an annual demand of 12,000kWh.
If electricity costs £0.13 per unit, Then, 4000kWh of electricity will cost approximately £520 per year for heating.
You now know how to calculate the running costs. So, if you want to calculate costs unique to your situation, you can substitute your specific values into the equation.
How Do Air Source Heat Pumps Work?
Even on a cold day, the sun warms the air around us. We can extract heat energy from the air using heat pump technology.
The ASHP normally sits in the garden of your home, protected from the weather, but open to the air. A fan draws in air from outside and uses it to slightly warm a refrigerant liquid, which turns into vapour. A pump uses electricity (either from the National Grid or from your personal power generator) to compress the refrigerant vapour. When pumps compress gases they become hotter. Then, the compressed gas condenses into a liquid again, thus releasing its stored heat. Next, the released energy heats water stored within a hot water cylinder. From here, we get the domestic hot water supply. The released energy also warms water in the central heating system which circulates the radiators in your house.
Air Source Heat Pump Reviews
Okay, we now know what a heat pump is, what it does, and how it can benefit us. But, which one should we choose? Let’s look at a few of the manufacturers who supply heat pumps in the UK and consider their products.
This company supply some of the most advanced heat pumps available. The popular model from this manufacturer is the Ecodan Monobloc PUHZ, which has an energy rating of A++ and comes in available outputs of 5, 8.5, 11.2 and 14kW. It is a self–contained unit and only needs to be connected to the water and electricity supplies. Operational temperatures can be as low as -25°C, it needs very little maintenance and is very quiet when running. A heat pump from this range costs between £2000 to £5000 for equipment only. Customer reviews suggest that it is quiet when operating, reduces energy bills and lowers carbon emissions.
This company’s popular model is the Daikin Altherma ERSQ AV1 that operates at temperatures down to -20°C. The heat pump has controllers that continuously adjust the compressor speeds to suit the demand, reducing the number of ‘stops’ and ‘starts’ that gobble up electrical power. Therefore, this feature reduces the domestic energy consumption by up to 30%.
It has an energy rating of A+ and is available in outputs of 11, 14 and 16kW. One of these heat pumps will cost around £2000 plus installation costs.
The EHS Monobloc, with an energy rating of A+++, comes in available outputs of 5, 9, 12, 14, and 16kW. It’s easy to install, is a compact and lightweight unit so can be wall–mounted as well as floor standing. The unit supplies water up to 55°C and operates in temperatures of -25°C. A typical price of one of these units retails at between £1800 to £4000, without installation costs.
The Nibe F2040 is a popular range with an energy rating of A+++ and comes with available outputs of 8, 12, and 16kW. The company is the leading manufacturer in Scandinavia, Poland and the Czech Republic. But, has offices in many other countries. They are easy to install and have a smartphone app allowing you to monitor operation automatically. If anything goes wrong with your machine, you’ll receive an automatic notification directly to your phone. A typical price for one of these heat pumps will be about £7000 plus the cost of installation. Customer reviews state that it’s easy to retrofit into existing properties, and customers notice a difference in their energy bills straight away.
How long does an air source heat pump last?
Even though most ASHPs have a guarantee for 5 years, they have a long lifespan of up to 20 to 25 years, assuming they have been maintained regularly according to the manufacturer’s instructions.
Should I leave my heat pump on all day?
There are conflicting viewpoints on the answer to this question. If you leave the heat pump boiler working constantly, even when you’re out at work, it will continue to work to keep the temperature at the pre-set level. In contrast, if you allow it to turn on and off at set times, say half an hour before you wake up or come home, the boiler works harder to heat the water from cold every time.
At what temperature do heat pumps become ineffective?
This varies depending on the brands and models, some of which have been specifically designed for efficient low–temperature operation. Some stop being efficient at around -10° to -15°C. While others can still work efficiently at -18° to -22°C. There are even some that will work efficiently at -25°C. However, the latter models usually require an auxiliary heater to slightly warm the air. The best advice, if you experience extremely low temperatures like these, is to consider using a Ground Source Heat Pump. These usually sit in a basement and extract heat from the ground below the permafrost level.
Do you need a boiler with an air source heat pump?
Yes, you need to have a working central heating system installed for an ASHP system to operate correctly.
How does an air source heat pump work in winter?
As the outside temperature drops, the efficiency of an ASHP will also drop. You would expect this to happen as there is less heat trapped in the air to extract. However, ASHPs can easily extract quite a lot of heat at temperatures commonly found in a UK winter. Typical Coefficient of Performance factors (COP) can range from 3.86 at 8°C down to 2.3 at –8°C. So, you see, you’re still harvesting a decent amount of energy even at that low temperature.
Can air source heat pumps provide hot water?
The answer here is definitely yes! However, there is a little snag. Most ASHPs can only heat water to a maximum of about 50°C. This is great as we don’t usually bathe in water hotter than 40°C. But, if you store water at less than 60°C, you run the risk of growing a colony of legionella bacteria in the system. Legionella can be fatal if you inhale infected water droplets, and that isn’t something we want to happen. Because of this, it’s good practice for installers to arrange for an auxiliary heater to increase the stored water temperature to above 60°C every day. The bacteria die within two minutes at this temperature and even faster if the temperature is higher than 60°C.
Can you run a heat pump on solar?
Definitely. Photovoltaic solar cells (or you could use wind turbines) are the perfect partner for ASHPs. Using electricity generated by these renewable sources will decrease your running costs and carbon footprint even more.
Find Local Heating Engineers
Installing an Air Source Heat Pump costs less than you’d think. Even if the initial costs are a bit pricey, you will soon recoup these with the amount you save on your heating bills. And, if you qualify for Government financial help, your costs will pretty much be covered over the first seven years.
If you want to know how much an ASHP will cost for your house, complete the form on this page and you’ll receive 2 or 3 quotes from qualified heating engineers.