AC BTU Calculator for Dubai and the UAE

BTU stands for British Thermal Unit. It is a measure of heat, and on an air conditioner it means how much heat the unit can take out of a room in an hour.

A 12,000 BTU unit removes 12,000 units of heat per hour. A 24,000 BTU unit removes twice as much.

You will also see tons. One ton of cooling is 12,000 BTU per hour, so a 1.5 ton unit is 18,000 BTU and a 2 ton unit is 24,000 BTU. Shops in the UAE use both words, and they mean the same thing.

The number you want is the amount of heat your room gains in an hour. Match the unit to that and the room stays comfortable without the machine working itself to death.

Most BTU guides online are written for mild climates. They will tell you to allow around 20 BTU per square foot, which is roughly 215 per square metre. Use that here and you will be cold in January and miserable in August.

Outside air of 45 degrees and higher for months means the difference between outside and inside is enormous, and heat pushes through walls, windows and roofs all day.

Humidity is the second half of it. An air conditioner does not only lower the temperature, it also pulls water out of the air, and that takes energy. Coastal humidity here means a real part of the unit is spent drying rather than cooling.

Sunlight is the third. Strong sun on a wall or through glass adds heat directly into the room, hour after hour.

That is why the starting figures in this tool are much higher than the ones you will find on a European or American site.

Two rooms of the same size can need very different units. These are the reasons, in order.

This is the mistake people make when they are not sure. They round up, thinking a larger unit will just cool faster and then relax.

It does cool faster. That is the problem.

An oversized unit pulls the temperature down quickly, hits the set point, and switches off. It has not run long enough to pull much water out of the air, so the room ends up cold and clammy. Then it warms up, and the unit starts again. This is called short cycling.

Short cycling wears out the compressor, which is the expensive part. It also uses more electricity than a right sized unit running steadily, because starting a motor costs far more than keeping it going.

A correctly sized unit runs for long stretches on a hot afternoon. That is what it is supposed to do. If yours never seems to switch off in August, that is often normal rather than a fault.

This calculator gives you a sensible number to shop with and to check a quote against. It is not a design.

For a single bedroom or a normal living room, it will get you close enough that the right unit is obvious.

Get a proper survey when the room is unusual: a double height space, a glass fronted majlis, a shop or a restaurant, or anywhere the whole property is being done at once. A survey looks at insulation, glazing type, shading, orientation and how the space is actually used.

It is also worth a survey if you are replacing a unit that never performed. Fitting the same size again repeats the problem, and the reason it failed may not be the size at all.