This technology is improving all the time so the efficiency of pumps is getting higher and the costs to buy and install them is becoming lower. At the time of writing this article the cost to install a typical air source heat pump is between £7500 and £12000. This figure will of course vary depending on where in the country the system is installed, the size of the heating system and the size of your property.
How quickly you start getting your money back from installing the heating system will depend a lot on the efficiency of the system and whether you have installed larger radiators or are using an ‘underfloor’ radiator system. The other important factor that determines the payback period is the type of fuel you are replacing.
Typical annual savings from using an air source heat pump compared to other types of heating in a standard four-bedroom house will be as shown in the table.
|Replacing this heating system||Annual saving|
|Oil combi boiler||£350 to £600|
|Gas combi boiler||£1900 to £2100|
|Electric night storage heaters||£600 to £1500|
Installing air source heat pumps (ASHP) as the primary heating source in modern houses is a growing trend in the UK today. For maximum benefit, this type of domestic heating must be used in conjunction with modern insulation methods. It is an ideal way of heating homes with no mains gas or if you already have an electric style heating system such as storage heaters and want to change to a more efficient way of heating. Air source heating systems harvest the heat in the outside air that has come from the sun and uses it to warm a low-temperature refrigerant. A heat pump compressor increases the temperature by compressing the refrigerant which is then allowed to evaporate so releasing its stored heat. This is a bit like a fridge working in reverse.
Benefits of Air Source Heat Pumps
There are many benefits to using air source central heating, such as:
- Easy Installation. They are easy to install compared to ground source heat pumps which need excavation in the garden. Although ground source heating may not be too difficult if the house is a new build, it still more expensive and will need more work than an air source.
- Low Maintenance. Air heat pumping systems need very little maintenance compared to gas and oil combi boilers.
- Intrinsically safer. Because you are not bringing a potentially highly flammable fuel into your home, there is less chance of dangerous accidents. In fact, the danger is similar to that from a domestic fridge being kept outside.
- Energy Efficient. These heating systems generate far less carbon dioxide than conventional fossil fuel heating systems.
- Renewable Heat Incentive Approved. The Renewable Heat Incentive (RHI) is a UK Government scheme to help with the cost of fitting renewable heating systems in your home. The air source heating costs qualify for the RHI which pays the homeowner for generating their own heat.
Although there are many benefits of using this type of heating system, they are not all sweetness and light. Here are a few of the disadvantages.
- Needs space. The external condensing unit requires space in your back garden. Although they are only about the same size as a domestic air conditioning unit, if you have a small garden, it will take up quite a substantial proportion of your recreational space.
- The condenser units can be noisy, especially if you live in a particularly quiet area.
- Cold pollution. Whereas normal machines can give off heat pollution, these can blow cold air into their immediate environment.
- Electricity usage. The equipment requires electricity to drive the pump. Although the electricity used is far less than would be required to produce the same amount of heat, the equipment still needs power to run it. It is therefore not considered to be a zero-carbon heating system unless the electricity is provided by a 100% renewable source such as a wind turbine or a photovoltaic solar panel.
- Winter back up. When the outside temperature reaches a specific low point (depending on the type of heat pump system), back up water heating elements will be required to keep the temperature at the required level.
The Two Types of Air Source Pumps
There are two sorts of air source heat pump systems used to produce heat:
- Air to Air Heat Pump: This takes the heat from the outside air and transfers it to your home using air ducting and fans. In the summer months, this type of heat pump system can work in reverse and provide cool air like an air conditioning unit. This method cannot produce hot water and is not commonly used in the UK.
- Air to Water Heat Pumps: This method takes the heat from the evaporated liquid and transfers it into a domestic wet central heating system. Because the heat is less than would normally be produced from a conventional boiler, the heating system needs either larger radiators or underfloor heating. This type is the best air source heat pump for UK users as it provides hot water as well.
In general, these heating methods can help to lower the country’s carbon footprint and reduce your heating bills as they use a natural energy source to produce the heat. Your actual carbon footprint (amount of carbon dioxide you use) will always depend on the type of fuel your heating system is replacing. For example, you will prevent more carbon dioxide from being produced if you are replacing an electrical heating system rather than a natural gas heating system. And you mustn’t forget that a heat pump needs an electricity supply to operate so unless you can provide this by a renewable source there will always be some carbon dioxide emissions.
Heat Pump Running Costs
Basically, the three main factors that affect the running costs of heat pumps are:
- The heat pump like all machines will not achieve 100% efficiency. When you are considering the heat pump system costs always look at the overall efficiency of the heat pump before you buy. Although the higher efficiency air source heat pump prices will probably be more than you expect, installing one will save you money when compared to the long term running costs.
- Amount of Heat – Obviously, if you set your thermostat to a higher indoor temperature the pump will have to work harder to produce that heat. This will cost more money than if you choose a lower temperature. Remember that with modern insulation practices there will be far less heat loss from the house so you shouldn’t need to produce as much heat as you would without the insulation.
- Temperature difference – The efficiency of the heat pump is calculated from the amount of work it has to do and this is related to the difference between the outside and inside temperatures. It is, therefore, cheaper to run the air source heat pump water heater if you keep it running at a constant lower temperature rather than continually turning it off and on. Similarly, it is better to keep the heating system turned on if you go away for a few days rather than turn it off and have to wait for it to warm up the house again on your return.
- Outside temperature – If there is more heat available for the heat pump to harvest, the pump won’t have to work so hard and its efficiency will be better. Unfortunately, this means that it is cheaper to run the heat pump in the summer when you don’t need warmth than in the winter when you do. There is an air temperature below which the heat pump will stop working for its own safety to prevent damage to the system. This bottom cut-off temperature will vary slightly depending on the model of the pump. What happens in practice is that a backup system of electrical elements similar to those in a traditional immersion heater hot water tank is fitted and these elements will help the system if the outside temperature becomes too low. For example, a common heat pump for use in cold climates is the Nordic Air Source Heat Pump. Using this pump, if the outside temperatures drop to -22° C (-8° F) then the system will rely 100% on back-up heat. Check the specifications of the heat pump before choosing the one to buy.
How Will Your Home Benefit?
After reading this article, many people will already be reaching for the phone to get their central heating system changed. Before you go any further, however, it is worth looking at a few points because not every home will benefit. Consider the following points and see if your house complies or can be made to comply:
- Do you have mains gas or do you rely on electricity, bottled gas (LPG), oil or solid fuel? Mains gas is fairly cheap so you won’t benefit too much. If you have any of the other fuels, which are so much more expensive, you will definitely benefit.
- Is your home well insulated? A home that retains the heat well with loft and cavity wall insulation, as well as double or triple glazing, will hold the heat much better than anything else.
- Has your home already got an underfloor heating system? If not, are you considering installing one? If the answer is yes, then this type of heating system is the best to have.
- Before even thinking about changing your heating system, make your home is as heat retentive as possible. Make it draughtproof, fit as much insulation as possible and replace all the external windows and doors with double or triple glazing. If you do these then your home will need very little heat to keep it warm and an air source heat pump will be ideal.
- Houses in the UK that are by the coast rarely experience very low temperatures so are more suited to this type of heating.
Hiring A Plumber
If you want air to water heat pump installed or even if you are interested in the air to air heat pump costs (remember that air to air only uses air ducts and will not provide hot water), you will have to consult someone who is skilled in fitting these kinds of technologies. A typical plumber who is brilliant at fitting other types of heating technology may not be that good at fitting this type unless he has been specially trained. If your heat pump has been poorly installed then you will have spent a lot of money and will not have any benefit from it. Make sure the installer is accredited by the Microgeneration Certification Scheme (MCS) if you want to be eligible for the Renewable Heat Incentive (RHI) as only MCS installers can be used.
Another thing to find out is whether the installer has had much experience in fitting these types of heating systems. Air source heat pumps are classed as a permitted development as far as planning permission is concerned so they should be exempt. It is always worth checking with the planning office first in case you come under any other restrictive covenants such as having a listed building or are living in a heritage area.
An air source heat pump and an associated system can save you a lot of money on your heating bills or it can be one of the biggest wastes of money you can imagine. It all depends on the state of the house’s insulation. It is always worth having an energy survey done before you decide to go for one of these heating systems and make sure that you do everything that can be done.
If your house satisfies the various requirements then you will have a lovely, warm home at a fraction of the costs of your previous heating system.