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Air Conditioner Size Calculator

How to calculate the size of air conditioner you need

Here you will find a calculator to help you work out the size of air conditioner you need for different room sizes, sizes are provided in BTUs (British Thermal Units), kilowatts, watts and HP (horsepower) or Peka (Dutch horse power).


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How big an air conditioner do you need?

It is important to select the correct size of air conditioner for a room. Too small and the air conditioner will be working too hard, the room will not be cool enough and you may get condensation problems. Too large and your air conditioner may be constantly switching on and off.

This is a simple calculator to help you decide what size of air conditioner you will need. This is based on the most commonly used air conditioners these days which are split units with a CoP of 4. CoP stands for Coefficient of Performance - how efficient the air conditioner is and modern air conditioners can move 4 kilowatts of heat by using only 1 kilowatt of electricity.

To find the size of air conditioner you will need enter your room size in metres:

metres long by metres wide = square metres.

The estimated size of air conditioner you will need is:

 
HP or PK
BTUs
Watts input
Well insulated room
Medium insulated room
Poorly insulated room

 

Standard air conditioner sizes available for domestic use:

The range of sizes varies between companies. Having said that they do tend to fall into specific preferred sizes. Generally speaking standard air conditioner sizes available for domestic use are:

0.5
HP
0.75
HP
1
HP
1.5
HP
2
HP
2.5
HP
4,800
BTUs
7,200
BTUs
9,600
BTUs
14,400
BTUs
19,200
BTUs
24,000
BTUs
373
watts
560
watts
746
watts
1120
watts
1,492
watts
1,865
watts

NOTE: These are the sizes quoted by manufacturers. When they quote sizes in HP or watts this refers to the input power the air conditioner uses, when sizes are quoted in BTUs this refers to the output ie. the amount of cooling achieved which is usually nearly 4 times the input power.

Size measurement in watts, BTUs horsepower and PK:

Different brands of air conditioners use different ways of indicating their size, for this reason 3 different size equivalents are given above:

1. HP or horsepower. Note that PK (pronounced peka) is Dutch for Horse Power which is the common sizing of air conditioners in Indonesia.

2. BTUs (British Thermal Units) the common sizing used in America.

3. The electrical power rating in watts (this is watts of input power not output watts).

Input power versus output power

It is important to note that the HP, PK and watts figures indicate the amount of power input, the BTU figures indicate the amount of cooling output achieved. The actual cooling achieved in BTUs depends on the efficiency of the air conditioner. The above figures are given as an approximate guide of what you might expect with normal modern air conditioners.

How insulated is your room? It makes a difference

Insulation makes a huge difference. The better a room is insulated the less air conditioning you will need. As a rough guide:

Well insulated room

A might have thick solid walls, an insulated ceiling, close fitting doors and few or double glazed windows and not many people in it.

Medium insulated room

A medium insulated room might have solid concrete walls, close fitting doors, an insulated roof and few standard windows.

Poorly Insulated Room

A poorly insulated room might have large window area, poorly fitting doors, a roof or walls that give off heat internally or a lot of people in it.


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