The answers, kept current
Almost every page you'll find about UK air conditioning was right when it was written. The rules changed twice in fourteen months, and most of them didn't. These say what changed, when, and where we got it from.
Start here
Nine so far, covering the questions that decide whether this is worth doing — whether you're allowed, what size you need, how loud it is, what it costs to run, and whether you're buying the right kind of heat pump at all.
Rules and permissions
Do you need planning permission for air conditioning?
Usually not. In England and Wales the one-metre boundary rule is gone and a stricter 37 dB calculation replaced it — but it is still 42 dB in Scotland, and the boundary rule still binds in Northern Ireland.
13 min read · 18 August 2026
Choosing
What size air conditioning unit do I need?
Start from floor area, then adjust for what the room actually is. And ignore the advice to go one size up — since May 2026 an oversized unit can cost you your permitted development rights.
9 min read · 18 August 2026
Choosing
How loud is air conditioning, really?
The indoor unit is quieter than your fridge. The outdoor one is the real question — and the decibel figure on the spec sheet is not the one the planning assessment uses.
8 min read · 18 August 2026
Costs
What air conditioning installation actually costs
Every other cost guide quotes a range, because the installers behind them price each job individually. Here are four fixed prices, and what sits inside them.
14 min read · 21 August 2026
Costs
What air conditioning actually costs to run
About 25p an hour in cooling. The more useful number is the heating one — roughly a quarter of what a plug-in electric heater costs for the same warmth.
8 min read · 12 August 2026Costs
Air conditioning against central heating
Cheaper per unit of heat, and not a replacement. The useful comparison is not which is cheaper but which is heating what, and when.
7 min read · 21 August 2026Costs
Is air conditioning worth it in a British house?
It depends almost entirely on whether you will use it as a heater. Here is how to tell which case you are in before you spend anything.
6 min read · 21 August 2026
Costs
The £2,500 air conditioning grant, and who actually gets it
£2,500, not £7,500 — and if you have a working gas boiler you almost certainly don't qualify. Who does, and what changed in April 2026.
6 min read · 12 August 2026
Choosing
Air-to-air or air-to-water? The honest comparison
One replaces your boiler, the other cools your bedroom. They're both heat pumps and they're rarely alternatives — and we only fit one of them, which is why this page tells you when to buy the other.
9 min read · 13 August 2026
Dated, sourced, and corrected when they’re wrong
Every guide carries the date it was last checked, the primary sources it was written from, and a plain note anywhere we haven't had it independently verified.
- Last checked
- Each guide shows its own date at the top.
- Sources named
- 25
- Legislation, standards and published data, listed at the foot of each guide with what each one establishes.
- Correcting something
- 6 of 9
- Guides that correct something widely published and now wrong.
Still published elsewhere, and out of date
The outdoor unit must be at least a metre from the boundary.
Removed in England on 29 May 2025. What decides it now is the noise calculation.
Planning permissionThe noise limit is 42 dB.
37 dB(A) under MCS 020(a) in England since 28 May 2026, and in Wales since 1 June. Scotland and Northern Ireland are still on 42.
How loud is it?When in doubt, go one size up.
An oversized unit can now fail the noise calculation and cost you permitted development.
What size do I need?
If we’ve got something wrong, we’d rather hear about it than rank for it.
We'll email you when the rules change
Twice in the last fourteen months the rules underneath this category changed: England’s noise standard on 28 May 2026, and Wales’s on 1 June 2026. When the next one moves, we’ll tell you what changed and what it means for a house like yours.
Or skip to the number
A few questions about the room gets you a price band, without reading anything.
Buy a system outright and the survey is included in the price. Book one on its own and it's £95, refunded in full against the order.