The UK government updated planning rules in November 2024 to bring heat pumps within permitted development in England, according to Nesta. The change dropped the "one metre rule" and allowed units that provide cooling alongside heating1. Permitted development means installation without a full planning application, subject to the conditions attached to the right.
The same account sets out where the right stops. Only detached homes may have two outdoor units under permitted development; all other property types need planning permission for additional units1. Nesta says this matters more for air-to-air systems than for air-to-water, because air-to-air installations are more likely to need two outdoor units to reach all the indoor units without long refrigerant pipe runs1. Leaseholders in flats will usually need freeholder consent to install an air-to-air heat pump, because of structural changes or external additions to the building1.
The planning change sits alongside a grant change. Nesta states that the Boiler Upgrade Scheme (BUS) is being expanded to include air-to-air heat pumps, with homeowners in England and Wales replacing a boiler with an air-to-air system "soon" eligible for a grant of up to £2,5001. Heat batteries are also eligible for the new £2,500 air-to-air heat pump grant1. Eligibility generally covers homeowners in England and Wales replacing fossil fuel heating systems, subject to property and installer criteria, and applications go through an MCS-certified installer, who typically handles the application1.
Nesta notes that air-to-air heat pump systems are not currently installed under the Microgeneration Certification Scheme (MCS), while installations eligible for the grant through BUS will likely require MCS certification1. It also notes that most air-to-air models do not usually provide hot water, so a separate system is needed, and that many households installing one keep their boiler for hot water, leaving roughly a quarter of their heat demand still burning fossil fuels1. An air-to-air heat pump typically costs between £1,500 and £4,000 per unit1. Air-to-air heat pumps are not yet widely used in British homes1.
"In November 2024, the UK government updated planning rules to include heat pumps under permitted development in England, in particular dropping the “one metre rule” and allowing units that provide cooling alongside heating"
Why it matters for households
For a household weighing up a heat pump, the planning change removes one of the steps that previously sat between a decision and an installation: in England, a unit that heats and cools can now fall under permitted development rather than a planning application, subject to the limits above. The limits are where the practical difference lies. A detached home can have two outdoor units under the right; a semi-detached house, a terrace or a flat cannot, and a second unit there needs planning permission1. For flats, freeholder consent is a separate hurdle that permitted development does not remove1.
The grant change affects the money side. A grant of up to £2,500 against a unit cost of £1,500 to £4,0001 changes the arithmetic on a per-unit basis, but the number of units a home needs, and whether hot water is covered, decide the total. Because most air-to-air models do not usually supply hot water1, a home that keeps its boiler for hot water is only partly off fossil fuels, and Nesta puts the remaining fossil share of heat demand at roughly a quarter1. Heat batteries being eligible for the grant1 speaks to that gap.
What happens next
Nesta describes the grant expansion as forthcoming rather than open, using "will soon be eligible"1. No start date for applications, and no date for any further change to permitted development for two outdoor units on non-detached homes, has been reported1. Nesta states that the Leasehold and Freehold Reform Act 2024 provides an opportunity to reduce challenges associated with freeholder consent, and that many aspects of the act will still require secondary legislation and consultation1.