Air-source heat pumps can provide fairly low-cost space heating for homes which are not connected to the gas grid, or for homes which are very well insulated. Amazingly, they can deliver up to 4 times as much energy as they consume.
Air source heat pumps are a kind of renewable energy technology which take the warmth from the air outside (even when it’s quite cold) and use it to heat the home. You can also get heat pumps that do the same thing using the warmth in the ground and in water, but air source heat pumps tend to be suitable for a wider range of properties. And because the air (or ground, or water) is heated by the sun, the energy that heat pumps produce is still classed as ‘renewable’, even though the pump itself is powered by electricity.
There are two types of air source heat pump. Air-to-water systems heat water which is then circulated around the home via radiators or an underfloor heating system. They can also be used to heat water in a storage tank for the bathroom or kitchen. Air-to-air systems typically use fans to circulate warm air around the home and cannot be used to heat water.
Another major advantage of Air Source Heat Pumps is that during the summer months they can be operated in reverse, like an air-conditioning unit, to provide cool air for your home.
How do they work?
Using various pieces of technical wizardry – namely an evaporator coil full of refrigerant fluid, a type of pump called a compressor and a heat exchanger – heat pumps absorb the warmth in the air outside and release this heat into air or water, which is then distributed around the home. They can do this even when the temperature outside is very low. Fridges work in the same way, only in reverse. They use the same bag of tricks to draw heat out of the air in the fridge, which is why the space behind fridge feels warm. The efficiency of a heat pump is measured by what is known as the Coefficient of Performance (CoP). This describes the maximum efficiency of a heat pump; the higher the CoP, the better. A heat pump with a CoP of 3 generates three units of heat for every unit of electricity it uses. A typical domestic air source heat pump has a CoP of 2 or 3, but remember this is its maximum efficiency; the actual ratio of ‘electricity in’ to ‘heat out’ over the course of a year will be a bit less.
Where do air source heat pumps work best?
Heat pumps make the most financial sense in properties which are off the gas grid and which therefore use expensive fuels like electricity, oil, LPG or coal for space heating. If you’re connected to mains gas, then you’ll
probably be better off with gas central heating. A well insulated home with high standards of air-tightness is also preferable. This is because heat pumps are most effective in homes which warm up quickly and are good at
keeping heat in. Heating systems powered by heat pumps operate at a lower temperature than ‘normal’ systems, so they need a distribution system that delivers heat over a larger surface area. Radiators connected to heat-pump systems tend to be big, but not very hot. Underfloor heating systems work particularly well with a heat pump. But in all cases, improving the energy efficiency of your home first will help you reduce your heating needs and in turn enable you to run a smaller and cheaper heat pump.
Finally, bear in mind that whilst the unit itself doesn’t take up a lot of space, they need to be positioned somewhere with adequate air flow. A space of approximately 2m2 is required, and this can be in a well ventilated loft as well as outside.
Integration with other renewable energy sources
Although an air source heat pump can meet the heating and hot water needs of an average household, you may also consider a back-up supplementary system, for example a solar thermal hot water system; and a wood pellet, chip or log stove could be integrated well. Solar water heating may provide all your domestic hot water needs during summer removing the need to run the heat pump at all, and so saving yourself the cost of the
The cost of air source heat pump unit can range from £5,000 to £10,000 and will depend on the size of the property it needs to heat. On top of this is the cost of the installation and of additional works required to upgrade
the distribution system (generally speaking installing a heat pump is not especially disruptive work). The running costs of an installed system will also vary depending on how much heat it needs to produce, what type of distribution system you have and the CoP of the system (see above).
The cost of the electricity used to run the heat pump for a typical three-bedroom semi-detached home is around £750 per year, and for a similar sized detached home £975 per year. This is much less than the cost of heating with electricity, oil, LPG or coal but likely to be more expensive than gas. Maintenance costs for air source heat pumps are low. They are reliable, work automatically and have a long life.
Advantages of Air Source Heat Pumps
- They are relatively easy to install
- Relatively low-cost compared to other types of renewable energy
- Can deliver up to 4 times as much energy as they consume
- ASHP can provide heating and hot water
- The equipment is unobtrusive compared to some types of renewable energy
- They can be used for air conditioning in the summer
- They require very little maintenance
- Relatively low running costs
- Air source heat pumps can generate less CO2 than conventional heating systems
Disadvantages of Air Source Heat Pumps
- Not all properties will save money by installing an Air Source Heat Pump – they are best suited to properties which currently use oil, coal or LPG as their heating fuel, or for homes which are very well insulated
- You’ll need enough space in your garden for the external condenser unit (comparable in size to an air-conditioning unit)
- You still need to use electricity to drive the pump, so an air source heat pump can’t be considered completely zero-carbon unless this is provided by a renewable source, such as solar power or a wind turbine
Air Source Heat Pumps are eligible for the Renewable Heat Incentive
If you are interested in installing an Air Source Heat Pump or just seriously curious, please complete the form in the green box to the right and request a FREE Renewable Energy Assessment or alternatively you can contact the Energy Saving Grants Team on 03302230333