I'm looking for an air conditioner for a big bedroom: 40 sq m and 4m high. I want to size it properly but struggling to find decent sizing information. There are some online calculators and rough rules of thumb but they produce wildly different answers. It doesn't help that different sources use different units and different assumptions.

Obviously the numpties working in the shops selling units have no idea. Surprisingly the manufacturers don't provide any sizing guidance.

Can anyone provide links to accurate sizing information or does anyone know of an installer they trust to get the sizing right?

Google has not been much help so far.

well that is 160 cubic meters right?
what else do they want to know?

Go for the 1.5hp unit, WJF - we did, and have no regrets. Slightly over-powered but better than having it struggle, and worth the extra $$$. Also, fork out for the invertor model (although others may argue this point). Happy to point out a supplier near Central Market if you're looking.

Thanks for the replies. Combined with those on the other forum and what the staff in various shops have told me it is clear there are as many (different) answers as there are people. 2hp is the closest thing to a consensus. Another thing that seems likely is units referring to hp are referring to the input power to the device, not the amount of heat it can move.
For now I'm going with the fan option. When I get round to working the size out accurately I'll reconsider.

General Mackevili wrote:Personally, I think a 1 hp is more than enough for what you're describing. One room, right?

I had a 1hp Panasonic Inverter and it was great. Never ever felt like it was over worked.

My buddy had the exact same model for a small apartment and it also worked fine for him.

And with 1hp and an Inverter model you will be spending next to nothing.

What do you reckon you were paying per day to run yours Gen and how many hours per day/night did you run it?

Cheers.

Thanks!