Air source heat pumps will revolutionise the way we heat our homes as gas boilers are phased out. With technology that avoids burning fossil fuels, air-to-water heat pumps provide low-carbon heating that cuts energy bills significantly. The popularity of heat pumps is already increasing, and this has resulted in more and more households wondering whether their property has room to install one.
This post explores the exterior and interior space requirements of an air source heat pump.
You’ll also find out about heat pump sizes, which, confusingly, aren’t the same as space requirements. And we’ll look at air source heat pump costs, savings and grants, to boot.
Air Source Heat Pump Space Requirements
Air source heat pump systems have two main components: an outdoor unit and an inside unit.
The external unit is known as a collector because it gathers warmth from outside air. It then transfers this heat to the indoor unit, called the air handler.
Unlike some other types of heat pumps, air source heat pumps don’t take up a great deal of space, either inside or outside your home.
Heat Pump Outdoor Unit Space Requirements
The outside heat pump unit is generally referred to as simply “the heat pump” because it’s the main part of the system.
It’s 1 metre to 1.5 metres high and 0.5 metres to 1 metre wide – taking up about the same amount of space as two washing machines.
Heat pumps are usually installed on the ground at the side or rear of a house and in close proximity to it. They can also be mounted on an external wall, near ground level.
Either of these options allows pipework to be kept to a minimum, making the system more efficient.
A heat pump also needs sufficient airflow, with minimal obstructions, in order to work at maximum efficiency. This means a clear area of at least 1.5 metres in front of the unit.
Alternative Heat Pump Locations
There’s not always enough space to put a heat pump in the ideal location.
For instance, the side of your house where you want to install the heat pump may have a pathway that’s too narrow.
In this case, if you have a flat roof, the heat pump could be installed there as long as it’s at least a metre from the roof edge. But access to it for maintenance will be more difficult.
Gardens provide a more common alternative location for a heat pump outside unit.
Heat Pump In The Garden
If you install a heat pump outdoor unit in your garden, it should be at least a metre from plants that would affect airflow. It must also be at least a metre from your property boundary in order to comply with heat pump regulations.
Keep in mind that you may have to cut back foliage regularly to keep it from encroaching towards the unit. And maintenance costs may be higher because the pipes are less accessible.
A further consideration is that a heat pump installed away from your house in the garden will need more pipework to reach the indoor unit. This will cause a certain amount of heat loss.
It’s recommended there should be no more than 15m of pipework between your house and the heat pump.
Heat Pump Indoor Space Requirements
Heat pump interior units are ideally installed close to the outdoor unit, usually on the wall. They need about the same space as a gas boiler. However, the main consideration when it comes to space is more likely to be the hot water cylinder.
You’ll need one of these if your air source heat pump is providing hot water supply as well as central heating. If you already have a cylinder, it will likely need replacing. Heat exchanger coils in standard hot water cylinders are generally too small to work with a heat pump.
The capacity size of the cylinder you need – how many litres it can hold – depends on the size of your house and its level of water consumption.
The average three-bedroom home needs a heat pump water tank that can hold around 180 litres. This would be around 1.3 metres high and 0.5 metres in diameter.
Some heat pumps also need a buffer tank.
Heat Pump Buffer Tank
A buffer tank is used in conjunction with the hot water cylinder and helps limit heat pump cycling – switching on and off to maintain a consistent indoor temperature.
It contains “black water” to supply a heating system such as radiators or underfloor heating.
A buffer tank needs to hold about 15 litres of water for each kilowatt of heat pump output.
So, a 10kW system needs a buffer tank with 150-litre capacity – about 1.2 metres tall with a diameter of 0.5 metres.
Radiator Space Requirements
A heat pump runs at a lower flow temperature than boilers and produces heat more slowly. This means larger radiators are needed.
To get the same amount of heat as a boiler generates, radiators fed by a heat pump may need to be up to around two and a half times bigger.
What Heat Pump Wattage Size Do You Need for Your Home?
The physical size of a heat pump obviously dictates how much room is needed to install it.
But the question of heat pump size can be confusing. Technically, it has nothing to do with the heat pump’s physical dimensions. Heat pump size refers to power output measured in kilowatts (kW).
When it comes to heat pump power capacity, bigger isn’t necessarily better.
You don’t want to pay more for a heat pump that produces more power than needed to heat your home and water. Running costs would also be higher because of loss of efficiency.
A heat pump home survey will enable your installer to size the system according to your home’s requirements.
Larger houses need a heat pump with higher power output. So do homes with poor insulation, so it’s a good idea to ensure your home is adequately insulated before installing a heat pump.
Typical air source heat pump sizes needed for a well-insulated property are:
- 4kW for a two-bedroom home.
- 5kW for a three-bedroom home.
- 9kW to 10kW for a four-bedroom home.
- 16kW for a five-bedroom home.
Why Heat Pumps Are Replacing Boilers
Homes in the UK account for around 14 percent of carbon emissions. That’s more than cars. This is largely because most households – around 23 million – use a gas boiler to provide central heating and hot water.
But as the country pushes towards its target of net zero carbon emissions by 2050, the days of heating our homes by burning fossil fuels are ultimately limited.
Boilers are already banned in 11 other European countries. Eventually, all gas boiler sales will be banned in the UK. The first stage is phasing out boiler installation in new-build homes. When this will happen remains unclear.
Meanwhile, the government is continuing to offer financial incentives to encourage homeowners to replace boilers with a low-carbon alternative such as a heat pump.
Heat Pump Costs, Savings And Grants
Installing an air source heat pump typically costs around £8,400 to £12,000-plus, depending on the size of your home.
But heat pumps pay for themselves by reducing energy bills by hundreds of pounds a year.
And government-supported grants cut installation costs considerably for low-income households who replace an old, inefficient boiler with a heat pump.
Up to £7,500 is available under the Boiler Upgrade Scheme (BUS). Heat pump funding is also on offer from the Energy Company Obligation Scheme (ECO4) and from local councils via ECO4 Flex (flexible eligibility) scheme.
Eco Grants can help you access a heat pump grant and figure out how much space your air source heat pump will need.