Guide · Updated 8 November 2026
Air to air heat pumps for flats and small homes
Flats and small homes are where air to air heat pumps make most sense. Many flats are heated by expensive electric or storage heaters and have no radiators or room for a hot water cylinder for an air-to-water system. One outdoor unit can feed two to five indoor units (a multi-split), and the £2,500 grant covers more than half of the government's typical £4,500 cost for a flat or small house.
Why they suit flats
- Replacing electric heating. Panel and storage heaters turn one kWh of electricity into one kWh of heat. A heat pump turns it into three to four or more.
- No radiators needed. No wet system to install.
- Small outdoor footprint. One compact outdoor unit on a balcony, wall or flat roof.
- Cooling. Top-floor and south-facing flats can overheat badly in summer.
Single split or multi-split?
| Single split | Multi-split | |
|---|---|---|
| Setup | One outdoor unit per indoor unit | One outdoor unit, 2 to 5 indoor units |
| Outdoor space | One box per room | One box total |
| Efficiency | Often slightly higher per room | Good; check the combined rating |
| If the outdoor unit fails | One room affected | All rooms affected |
Under permitted development in England, a block of flats is allowed one unit, so a multi-split is often the only practical choice for a flat.
Before you start: permissions
- Freeholder or managing agent: leaseholders almost always need written consent to fix anything to the outside walls.
- Planning: for flats, the outdoor unit must be no bigger than 0.6 cubic metres to be permitted development. See our planning guide.
- Building rules: some blocks restrict anything on balconies or facades.
Hot water in a flat
If your flat has a gas combi boiler you plan to remove, you'll need another way to heat water, such as a compact electric cylinder or a hot water heat pump. If it already has an electric immersion cylinder, that can stay.
Replacing storage heaters and the grant
Replacing electric storage heaters counts: the Boiler Upgrade Scheme covers homes replacing electric heating. The system must be able to meet the whole flat's heating needs, which a multi-split covering the main rooms often can, with small electric heaters allowed as top-up in rooms like the bathroom.
Questions
Can I have an air to air heat pump in a flat?
Usually, yes. You'll need the freeholder's permission if you're a leaseholder, and in England the outdoor unit should be no larger than 0.6 cubic metres to be permitted development.
Can I replace storage heaters with an air to air heat pump and get the grant?
Yes, if you're in England or Wales, the system can meet the flat's heating needs and the installer is MCS certified for air to air. Replacing electric heating is eligible.
Sources
- GOV.UK: Discounts for families to keep warm in winter and cool in summer (18 Nov 2025)
- Ofgem: Summary of updates to BUS guidance for installers, March 2026 (air-to-air eligible from 28 April 2026)
- Planning Portal: Heat pumps
- TechRadar: Air conditioning isn't banned, the planning rules explained (Jul 2026)
Checked 8 November 2026.