First look at your cooling needs

For a small room, under 200 square feet, look for a unit with 7,500 to 9,000 BTUs (British Thermal Units)

For a medium room, 200 to 300 square feet, 9,000 to 12,000 BTUs

For a large room, 300 square feet and over, make sure you get a unit that can handle the volume, 12,000 BTUs and more.

The BTU measurement indicates how much heat you can remove per hour. Portable air conditioners need more BTUs to cool your space than one fixed in your window.

Is the room receiving direct sunlight or is it in the shade? If your room receives some morning or afternoon rays, know that it will take more to cool your room than if it is in the shady side of the house.