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So when Londoners ask “should I get a heat pump or air con?”, the honest answer is: you’re not choosing between two technologies. You’re choosing between wet and dry.So when Londoners ask “should I get a heat pump or air con?”, the honest answer is: you’re not choosing between two technologies. You’re choosing between wet and dry.

AC and Heat Pumps: Wet vs dry

Air-to-water (the “heat pump” everyone means). Big box outside, connected to your radiators, underfloor heating and hot water cylinder. Replaces your gas boiler entirely. Heats the whole house beautifully. Cools absolutely nothing – you cannot get cold water out of your radiators without your house turning into a condensation swamp.

Air-to-air (the thing your neighbour calls “air con”). Box outside, one or more slim units on the wall inside, blowing air. Heats and cools. Doesn’t touch your hot water. Doesn’t need a single radiator.

That’s it. That’s the whole fork in the road. One warms your building’s plumbing. The other conditions the air in specific rooms – in both directions.

Lets talk money

Grants. The Boiler Upgrade Scheme still hands over £7,500 for an air-to-water heat pump — but since 28 April 2026 it also offers £2,500 for air-to-air systems. Yes: the government now part-funds air conditioning.

Two enormous caveats, though:

1. The air-to-air grant is aimed at homes replacing direct electric heating – storage heaters, panel heaters, that sort of thing. If you’ve got a working gas boiler, don’t get your hopes up.
2. In practice it has barely functioned yet. Certification paperwork and an empty MCS product directory have jammed the pipeline, and only a few dozen vouchers had been claimed by mid-2026. Ask an installer where things stand before you build a budget around it.

	Typical UK	London reality
Single-room split (air-to-air)	£1,500–£3,000	add 20–30%
Multi-split, 3–4 rooms	£3,500–£7,000	add 20–30%
Whole-house air-to-water	£11,000–£14,000	before the £7,500 grant

Running cost. At the current price cap, electricity is about 26p a unit and gas about 7p. That’s a ratio of roughly 3.5 to 1 – which means a heat pump has to squeeze 3.5 units of heat out of every unit of electricity just to draw level with your boiler. Good ones manage that and a bit more. So: cheaper, but not the halving of your bills that some brochures imply.

For cooling, a decent inverter split costs somewhere around 10–30p an hour. A portable unit dragging a fat hose to a half-open window costs roughly double that and cools half as well, which is the great British summer tragedy in a sentence.

Does being in London make a difference?

Three things make this a genuinely different question inside the M25.

One: it’s hotter here. The urban heat island means parts of London run up to 7–10°C warmer than the surrounding countryside. City Hall reckons around a million London homes are at high risk of overheating. Central boroughs full of flats fare worse than leafy outer suburbs full of houses. Meanwhile only about 5% of British households have any air conditioning at all versus 25% in France.

Two: planning is now dramatically easier. In May 2025 the permitted development rules for England were rewritten. The old rule forcing units to sit a metre from your boundary was scrapped. The size cap jumped from 0.6m³ to 1.5m³ on a house. Detached houses can have two.

Three: London will still find a way to make it complicated. Permitted development evaporates if you’re in a conservation area (which is a lot of London), listed, or under an Article 4 direction. Flats get a tighter 0.6m³ limit. And if you’re leasehold, your freeholder’s opinion outranks the entire Town and Country Planning Act. Check the lease before you check the planning portal.

There’s also a policy tension worth knowing about: the London Plan actively discourages “active cooling” in new developments, on the grounds that air conditioning dumps hot air into a city that’s already too hot. The Mayor’s Heat Ready London plan leans hard on shading, greening and retrofit instead. Nobody’s coming for your split system but don’t expect the planning system to cheer you on.

So what should you do?

Victorian terrace, working gas boiler, one bedroom that becomes a kiln in July. Don’t rip out the boiler. Put a split unit or two in the rooms that suffer. You get cooling now and a bit of cheap shoulder-season heating as a bonus.

Flat with storage heaters. This is the sweet spot. Air-to-air heats better than your storage heaters, cools in summer, and is the one scenario the £2,500 grant was designed for. Freeholder permission is your main hurdle.

You want off gas entirely. Air-to-water plus the £7,500 grant. Accept that it won’t cool, and solve summer separately.

Rented, skint, or the flat’s tiny. External shading beats everything. Blocking sun before it hits the glass is roughly ten times more effective than chilling the air after it arrives, and costs about a hundredth as much. Add night ventilation. Then, if it’s still unbearable, buy the machine.

Five questions to ask any installer

1. Are you F-Gas registered? (Legally required for refrigerant work — no exceptions.)
2. Are you MCS-certified, if I’m chasing a grant?
3. What’s the noise level at my neighbour’s nearest window?
4. Where exactly does the outdoor unit go, and does that keep me inside permitted development?
5. What’s the SCOP, and what did you assume about my insulation to get there?

Get three quotes. Always three.