About AirconCalculator

AirconCalculator is an independent UK resource that helps homeowners, renters, and small businesses size and choose air conditioning. We are not a retailer or manufacturer — our goal is simply to give you accurate, plain-English information.

What we do

Choosing the right air conditioning unit is harder than it looks. Undersized units run continuously and never cool the room properly; oversized units short-cycle, waste energy, and leave the air feeling clammy. Our free calculators help you arrive at the right BTU figure before you spend a penny, and our guides explain the trade-offs between portable, split, and multi-split systems in plain language.

Our editorial approach

We try to be transparent about how we reach our conclusions. In practice that means:

  • Documented methodology. Our BTU calculator follows the same heat-load principles used by HVAC engineers — ceiling height, glazing, orientation, occupancy, and equipment load are all factored in. The assumptions behind each figure are explained on the calculator page itself.
  • Dated energy figures. Electricity unit rates change frequently. Wherever we quote a pence-per-kWh figure we state the source and the date it was last verified. Check that date before using it for a real budget.
  • Honest product coverage. We do not publish "top 10" lists driven by commission rates. Products appear in our round-ups because they performed well against the criteria we set out at the start of each article.
  • No hidden sponsorship. We are not paid to feature any brand. If that ever changes we will say so clearly at the top of the relevant page.

How the calculators work

The BTU calculator uses a simplified heat-load model. It starts from the room volume, then applies adjustment factors for solar gain (south-facing rooms need more capacity), glazing area, insulation quality, and the number of occupants. The method is conservative — it errs on the side of slightly higher capacity rather than under-speccing. Full details are on the calculator page.

The running-cost and efficiency calculators use the unit capacity and manufacturer-stated SCOP/EER figures you provide, combined with the current electricity unit rate. All intermediate values are shown so you can check the maths yourself.

Affiliate links

To keep the site free we use affiliate links on some pages. If you follow a link to a retailer and buy something, we may earn a small commission at no extra cost to you. This never influences which products we cover or how we rank them. For full details see our affiliate disclosure.

Get in touch

Found an error, have a suggestion, or want to ask something not covered by the FAQ? Visit our contact page.