Air conditioning buying guides
Everything you need to choose an air conditioner and keep the running cost down — starting with the number that matters most, cost per hour to run.
BTU calculator Work out the right cooling capacity for your room. → Running cost calculator Cost per hour/day/month/year for any unit, at your rate. →
Running cost & savings
- How much does it cost to run an air conditioner? The cost-per-hour formula, typical UK & US costs, and how to cut your bills.
- Do air conditioners use a lot of electricity? Watts by type, cost per hour/day/month, and the easiest ways to cut the bill.
- How to reduce air conditioner running costs 9 changes ranked by impact — setpoint, sizing, efficiency, filters — with the rough % each one saves.
- What’s a good cost per hour? Benchmarks by type Cost/hr, watts and EER/SEER ranges by AC type — judge whether a unit is efficient or a money pit.
Choosing & sizing
- What size air conditioner do I need? BTU by room size Match cooling capacity to your room in m² or sq ft — and avoid wasting money.
- Air conditioning for a conservatory Solar gain means you must oversize — how much extra BTU, portable vs fixed, and the venting problem.
- Air conditioning for a server room / home lab Size by equipment heat load (watts → BTU), not floor area — plus the 24/7 running-cost maths.
- Are portable air conditioners worth it? An honest look at running costs, the pros and cons, and when a portable makes sense.
- Can I plug an air conditioner into a normal socket? Watts-to-amps for UK 13A and US 15A/20A circuits — and which AC types are plug-and-play vs need a dedicated circuit.
- Can you install an air conditioner yourself? DIY feasibility by type, the certified-installer rule for refrigerant, and typical install costs.
Compare the types
- Which air conditioner type should you buy? Start here: a decision guide across all four types, linking every head-to-head comparison.
- Portable vs window air conditioner The two no-installer options — which is cheaper to run, and which your windows allow.
- Portable vs split air conditioner Plug-and-play flexibility vs the lower running cost of a fixed split — with the break-even.
- Portable vs mini-split air conditioner The biggest running-cost gap of any pairing — convenience vs efficiency.
- Window vs split air conditioner DIY window unit vs the quieter, more efficient split — and when each pays off.
- Mini-split vs window air conditioner Cheap and self-installed vs efficient, silent and permanent — the numbers.
- Split vs mini-split: what's the difference? Ducted vs ductless, single- vs multi-zone — the terms decoded, with running cost.
Efficiency & technology
- SEER vs EER: efficiency ratings explained What EER, CEER, SEER and SEER2 measure — and how each maps to running cost.
- Inverter vs non-inverter: which is cheaper to run? How inverter compressors cut running cost 30–50%, with the payback maths.
- Single-hose vs dual-hose portable AC Why single-hose units fight themselves with negative pressure — and the 20–40% efficiency gap.
- Can an air conditioner heat your home? Reverse-cycle heat pumps, COP/SCOP, and why a COP of 3–4 beats electric and rivals gas.
- Refrigerants explained: R32 vs R290 vs R410A GWP, efficiency, flammability and phase-out — what the refrigerant means for efficiency and future servicing.
Air conditioning vs the alternatives
How we rank
Or jump straight to air conditioners ranked by cost to run.
