It can be tricky to pick an appropriate air conditioner to suit your needs. Here are two tips for getting the right outcome in terms of the capacity and efficiency of the model you install. Choosing The Right Capacity The power, or capacity, of an air conditioner is determined by its kilowatt output. It's critical to select an air conditioner with the appropriate capacity for the area to be cooled. If you get one too powerful, you'll pay higher running costs and possibly a higher purchase price as well.