An air source heat pump (ASHP) works by transferring heat absorbed from
the outside air to an indoor space. This heats the radiators and provides
domestic hot water via a wet central heating system. Heat pumps work like
refrigerators: they absorb heat and transfer it to another medium.
Some air source heat pumps can also be used as cooling systems in
summer. The most common is to place them outside a building with enough space
How does an air source heat pump work?
An air source heat pump works much like a refrigerator running in
reverse to heat your home. Here's how it works:
1. Outside air is blown through a network of pipes filled with refrigerant.
This causes the refrigerant to heat up and change from liquid to gas.
2. This gas is passed through the compressor, which increases the
pressure. Compression also adds more heat - similar to how an air hose heats up
when you inflate a tire.
3. The compressed hot gas enters the heat exchanger surrounded by cold
air or water. The refrigerant transfers its heat to this cold air or water,
making it warmer. This circulates in your home to provide heating and hot
water. At the same time, the refrigerant condenses back to the cold liquid and
starts the cycle again!
Is an Air Source Heat Pump Right for My Home?
ASHP can be installed in a variety of properties, whether small or
large, rural or urban.
An air source heat pump is right for you when:
1. You are looking for a low carbon, environmentally friendly and
sustainable way to heat your home
2. The property is well insulated - this is important to improve
efficiency and keep operating costs low
3. Insufficient outside space required for ground source heat pumps –
typically three times the gross floor area of the property. For ASHP, all you
need is space to mount the unit to the exterior wall with enough space around
for good air flow
4. You are installing or have installed a floor heating system. Air
source heat pumps are particularly suitable for floor heating as they are most
efficient at producing low water temperatures
Both new and existing properties can benefit from the energy saving
capabilities of heat pumps.
What to Consider When Upgrading to an Air Source Heat Pump?
Most homes will require some adjustment to use a heat pump. They're
great for keeping your home warm, but you may need to take steps to prevent
heat loss for optimal running costs.
Advantages of air source heat pump
1. Efficient production of heat and hot water
2. Zero carbon if used with renewable tariffs
3. Can closely match the operating costs of other home heating systems
4. Boiler upgrade programs can offset installation costs
5. They are easier to install than ground source pumps that require
digging in the garden
6. Low maintenance cost and long service life
7. Some systems can provide cooling in summer
Disadvantages of Air Source Heat Pumps
1. Your radiator will feel warm, not hot to the touch
2. Best for keeping environments warm, but not for adding heat
3. Keep the heat in - consider upgrading your insulation to keep running
4. Installation may take 3 - 8 days
5. You need space - outside for the pump as the air needs to circulate
and inside for the storage tank
Are there different types of air source heat pumps?
Yes! There are two main types of air source heat pumps, "air to
air" and "air to water". Most air source heat pump units in the
UK are of the so called "air to water" type.
1. An air-to-air heat pump, which takes heat from the outside air and
sends it directly into your home through a fan system to heat the room.
2. Air-to-water heat pumps, which take heat from outside air and
transfer it through your central heating system to provide hot water heating,
radiators, or underfloor heating in indoor spaces (or all three).
How much does an air source heat pump installation cost?
Air source heat pumps cost more than new gas or oil central heating
systems. Typical costs range from £4,000 to £8,000, depending on the pump brand
and its heat output.
You will also need to pay for installation. This could bring the total
to £5,000 to £10,000. If you're installing a new underfloor heating or air
distribution system, you'll also need to consider these costs. And may improve
insulation, as air source heat pumps are not very effective at heating
ventilated or poorly insulated homes.
How much does an air source heat pump cost to run?
Air source heat pumps are one of the most efficient home heating
appliances on the market. Traditional boilers run at 90% efficiency, and you
lose 10% of the heat produced by burning fossil fuels. On the other hand, heat
pumps have an efficiency rating of around 350%. We expect fuel prices to
rebalance in time, which will bring running costs on par or even less than what
you would typically pay for your existing heating system. When you're weighing
environmental benefits against fossil fuel options - a heat pump is the better
Example of operating costs for a modern four-bedroom residential air
source heat pump
Energy prices vary - and so does our home and energy use. So it's hard
to give an exact number on how much you can save in a year. But, based on some
industry-wide data, we've put together this example.
A modern four-bedroom house may require around 19,000 kWh of heat per
year (though this will vary).
1. This will cost around £884 for gas (90% efficiency; gas costs 4.65
kWh times 19,000 kWh).
2. Oil home is around £916 (oil boiler is 90% efficient; fuel cost is
4.82kWh times 19,000kWh)
3. LPG home is around £1,463 (boiler efficiency is 90%; LPG cost is 7.70
kWh times 19,000 kWh)
4. The cost of using an air source heat pump and electricity at
20.06p/kWh is £1,089 (20.06p/kWh divided by the heat pump COP of 3.5,
multiplied by 19,000kWh).
Are there maintenance costs for air source heat pumps?
Air source heat pumps use proven technology and may have an operating
life of 20 years or more. But just like a boiler, you should have your air
source heat pump professionally serviced every two or three years (or yearly,
if the manufacturer recommends it) to ensure it's still in top condition. You
can do some things yourself:
1. Make sure there is an adequate air supply. This means regularly
checking the fan grills for leaves or debris. And trim any plants that get too
close to the equipment or its pipes.
2. In very cold weather, remove snow from the air source heat pump and
check that the grill is not blocked by ice.
3. Let the heat pump run as suggested by the installer, it may take some
getting used to - but the heat pump works best if left alone.
How to get an air source heat pump?
Air source heat pumps are best for well-insulated homes and are best
used with technologies such as underfloor heating. Your home also needs to have