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AC sizes and types

In this article you will learn two things:

  • What are the different types of Air Conditioners
  • How to use BTU and TON to work out the correct size of Air Conditioner you need

There are four main types of air conditioners.

1) Split air conditioners

Ductless, mini-split air conditioners are the most popular type of air conditioner in use today. These consist of an outdoor unit containing the compressor and an indoor unit that controls and disperses the air. They can be conveniently installed in houses that have already been built or where only individual rooms need to be cooled. Their greatest advantage is they use the least amount of energy, so saving you money on the electricity bill.

2) Window air conditioners

Window mounted air conditioners are relatively compact units that fit conveniently in windows, cooling by releasing hot air from the back while injecting cold air into the room from the front. These are most suitable for smaller spaces which they can cool with greater effectiveness. While old window rattlers are now a thing of the past thanks to the latest technology, window air conditioners are less efficient than split units.

3) Central air conditioning

Central air conditioners consist of a large system of a cooling unit attached to a large system of ducts that supply cool air and return hot air from different rooms. It is a very popular solution in situations where entire houses or building need to be air conditioned. However, central air conditioning is not as energy efficient as split or window air conditioning.

4) Portable air conditioner

Portable air conditioning units have evolved from window air conditioners. They work by taking in the hot air from the room, cooling it and releasing it back into the room. A hose that runs from the unit to the window takes excess hot air outside. While the solution is very convenient, it is not as effective or as efficient as the other types on the market.

What does BTU mean for Air Conditioners

British Thermal Unit, or BTU, is used to measure an air conditioner’s capacity.

One BTU is the energy required to raise the temperature of a pound of water by 1°F.

It is very important that the BTU of the unit you choose matches the size of your room. How many BTU should the air conditioner have? A simple rule of thumb is to multiply the square feet of the room by 25. This will give you the amount of BTU you should be looking for in your air conditioner.

We Measure the size of an Air Con unit by using BTU and TON

When considering the BTU of an air conditioner, it’s crucial not to get an underpowered unit.

Such a unit would labor to cool the room without being able to effectively get the job done. This will have an adverse impact on the energy consumption of the air conditioner and also shorten its lifespan.

It may seem like a good idea to go in the opposite direction and get a more powerful unit than is required, but this is not better either.

Such an air conditioner will be surplus to requirements and consume more electricity than is necessary to cool a room. Furthermore, since an air conditioner also dehumidifies a room, a more powerful air conditioner will operate for a shorter duration and leave more humidity in the air, impacting on your comfort. Consequently, it is vital to stick to the recommended air conditioner capacity for optimum efficiency and effectiveness.

What does TON mean for Air Conditioning

A one ton block of ice in terms of BTU

A TON represents the overall cooling capacity of an air conditioner.

This measurement dates back to when people used actual Ice to cool down rooms. Simply stick a block of Ice in front of a fan and Voila! – Your room is ever so slightly cooler!

The ice block absorbs the heat from the air and in return it melts. You can accurately measure how much heat a given block of ice can absorb before it melts. That measurement is called the ‘Latent heat of fusion’ and in imperial units tht figure is staggeringly high at 143 BTUs per pound. Meaning that tiny 1 pound block of ice can actually absorb a lot of heat before it eventually melts.

So we have carried this calculation forward to modern times and our new fangled technology:

One TON = A One ton block of ice!

And that measurement above still holds true. A one ton block of Ice requires 288,000 BTU of heat in a 24 hour period in order to fully melt.

You may have seen different sizes of air conditioners labeled as a ‘one ton unit’ or a ‘two ton unit’. Well, using our calculation we know that a one ton unit can absorb 288,000 BTU in a 24 hour period, or 12,000BTU per hour and the caclulation simply doubles for each ton you add. A two ton unit is rated as 24000 BTU per hour, a 3 ton unit = 36000BTU and so on.


So, now you know what a TON and a BTU represents and how to use that calculation in order to match it up to the size of room you want to cool. By using a simple BTU calculator – you can feed it the sq ft of the space you wish to cool and it will tell you the size (in BTU) of air conditioner you require.

This article was written by Julia Montague – check out her author bio here