An air source heat pump needs not only enough space for the unit itself, but also sufficient space around it for air to be drawn in and expelled efficiently. This means that there is no set answer for how much space is needed, as ultimately, it depends on the unit size. Furthermore, it’s not just about the space you need outside; you may also need room indoors for the hot water cylinder.
In this blog, we explore how much space you may need for your air source heat pump, why it matters, and whether your property is likely to have enough space to accommodate one.
Outside, an air source heat pump doesn’t take up much space (typically 1- 2 m²), so its footprint is quite small. However, you do need to ensure there is suitable space around the unit for maximum airflow. This normally means you need to account for the unit space as well as space for airflow all around the unit.
This clearance ensures your unit pulls in enough air and expels it too. When choosing an air source heat pump, just ensure that you can:
Indoors, you will need enough space to house a hot water cylinder. It’ll normally be placed in a garage or airing cupboard, for example, and should take up roughly the same space as a standard water cylinder. However, in larger homes, you may need a larger tank to heat the property efficiently. Your engineer will be able to advise on the best location, heat pump and water cylinder for your property.
In most cases, you’ll be able to have an air source heat pump installed at your home. However, each property is different, and the ideal location or size of a heat pump varies between property types.
| Property Type | Can I have a heat pump? | Considerations |
| Detached | Yes | Ensure suitable space indoors & outside |
| Semi-detached | Yes | Pump should fit behind the home or at the side |
| Terraced house | Yes | More limited space, so check your home meets requirements for optimal use |
| Flats & apartments | Sometimes | Limited space, potential reduced efficiency. Freeholder rules may restrict installation |
You can position your heat pump almost anywhere outside your property, but your installer will find the most suitable location for efficiency, noise and accessibility. Common locations include:
Whilst you may prefer the heat pump on the side of your home, if sufficient space isn’t available to maximise airflow or to hold the unit, your engineer will advise on a more suitable position. They’ll look for plenty of external clearance, no plants or greenery that can obstruct it, easy access for servicing, and minimal vehicle traffic passing it. Just remember to keep the unit clear of bedroom windows; the low hum at night can resemble that of a fridge or freezer and could stop you from sleeping!
No, in most cases you won’t. Installing an air source heat pump is normally within permitted development; however, rules changed in May 2025, and where you can put your unit now is based on noise, rather than distance from your boundary.
This means:
Despite these changes, other rules do apply. On flat roofs, for example, all parts of the heat pump must sit at least one metre from the external edge of the roof. For those living in flats, units are capped at 0.6 m³ and can only be installed with freeholder or management company permission.
As with most planning permission rules, listed buildings, conservation areas and those under Article 4 Direction sit outside permitted development, so speaking with the local planning authority first is essential.
Smaller properties or those that are well-insulated may need a 5-8kW heat pump, whereas a larger property, or one that isn’t well insulated, may benefit from 12-16kW or more.
However, several factors will determine the heat pump you need for your home.
Just bear in mind that each of these can affect the size and cost of your air source heat pump, but our Sussex-based team can use this information to find the most efficient and cost-effective heat pump for your property.
In many cases, it’s best to go a little too big rather than a little too small. That way, your heat pump doesn’t work too hard in the colder months and, when there is a sudden rush on the hot water, the unit can handle the added demand. However, going too big or too small also presents challenges:
The minimum space needed for a heat pump depends on the unit size itself. For whatever size unit you have, you’ll need to consider suitable clearance around it for optimal airflow. Fitting a large unit into a small space will greatly reduce its efficiency and strain the unit, potentially leading to costly repairs.
For a hot water cylinder, you’ll normally need approximately 80 cm x 80 cm space, but this can vary by property. You’ll only need the cylinder if your air source heat pump heats water as well as the air. If you already have a cylinder, replacing it with one that’s compatible with a heat pump should not cause any space issues.
If, however, you have a combi boiler and your air source heat pump is replacing it, you’ll now need to consider where the cylinder can be placed.
You might. Not every heat pump needs one, but many do, and when required, they take up similar space to a hot water cylinder. These tanks are insulated vessels that hold extra heated water; think of it like a battery for your heating system.
It plays two roles:
If your heat pump is a fixed-output pump, it will need a buffer tank, but inverter pumps don’t normally need one unless different rooms are set to different temperatures.
A buffer tank can be stacked above or below the hot water cylinder, combined with it in a tall vessel or put in a loft or basement.
Considering a heat pump to help reduce your energy bills? Speak to our team at Sussex Air Conditioning & Heat Pumps Ltd. Our team of qualified engineers is on hand to provide air source heat pump installation in Sussex. We’ll carefully assess your property and establish the optimal size and placement of your unit for maximum efficiency and performance. Contact us today to find out more.
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