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Air Conditioning Calculatoer

Please try our cool sizing calculators to help you select the best portable to make you Comfee. 

STEP 1: Check the cooling power is large enough (Size kW)

​To ensure that you select a product with enough power to cool down your room, you need to consider all of the things within the room that produce heat. The heat output of items can be measured in watts, 1000w = 1.0kW


​For every watt of heat that is warming up your room, you will need a watt of cooling to reduce the temperature i.e The heat from 1 person is approx 120w, a tv approx 80w, lights 100w and many other products that warm up a room such as ovens, refrigerators, outside air and sun-facing windows/walls, etc.

This is a science that we can help you with but for domestic cooling requirements, you can make some assumptions. These are guides based on average amounts of watts that warm a room based on its dimensions. Approximate Watts of heat for every m2 based on room use. (Please also see footer notes)  

Bedrooms: +80W/m2 based upon 2 persons a TV and some lighting. (small window)

Living Room a: +120W/m2 based upon a family of 4, large TV, and living room lighting.
(average window)

Living Room b: +140W/m2 based upon a family of 4, large TV, and living room lighting. (large window) 

Studio: +160W/m2 based upon a family of 4, large TV, kitchen area, and essential appliances. (medium window)

Sun Room: +180W/m2 this based on an amount of roof glazing (25%) that is not shaded from the sun.


If your room has more than average amounts of warmth from other factors such as sun-facing large glass panels, patio doors, etc please increase your W/m2. If you are unsure please give us a call, we are here to help.

​After estimating your cooling needs please check the size of your portable to make sure it is large enough.​

STEP 2: Check the fan is powerful enough (Size m3/h)

One overlooked requirement of air conditioning is how powerful the fan is. How many times you can get the room's warmer air to pass through the portable cooling coil is essential. The term used is air changes per hour.​

​Sound complicated? It's not, and it is actually one of the best checks of an air conditioner size that you can do. 


​How much air is in the room? (Length  x Width x Height) x the number of air changes you need.

The calculation is made even easier by the airflow guide on this page.​

All you need to think about is the more times the air passes through the cooling coil in every hour, the faster the portable will cool all of the air in the room, this lowering the room temperature. ​

If your portable air conditioner cannot change the air at least 5 times an hour then it will not be effective. 

​A guide to how many air changes you should look to achieve is below:​

Bedrooms: +6 Air Changes Every Hour. (conditions as above)

Living Room a: +6 Air Changes Every Hour. (conditions as above)

Living Room b: +7 Air Changes Every Hour. (conditions as above)

Studio: +8 Air Changes Every Hour. (conditions as above)

Sun Room: +10 Air Changes Every Hour. (conditions as above) 

Please now check the maximum airflow of your portable to ensure it is powerful enough. ​

Please note: No 2 rooms have identical heat output, the above information is for guidance only and is not a full heat gain assessment of your cooling needs.  

Please note: For the portable air conditioner to operate effectively the heat from the room must be fully exhausted via an air duct to outside. (1.5m supplied)

If the room you are cooling has a height of more than 3.5m or requires more than 3.5kW of cooling; please do not buy a portable air conditioner. 

If your requirements are not catered for above, your money would be better spent on a professionally installed air conditioning system.

We can recommend professional, fully qualified air conditioning FGAS installers local to you. Call us to find out more.

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