The window air conditioner you choose must have roughly 20 British Thermal Units (BTU) of cooling per square foot of room space. Measure the square feet of the room’s floor and multiply that by 20.

1. Midea 5,000 BTU Mechanical Window Air Conditioner If you only need to cool down a small to mid-sized bedroom, Midea’s 5,000 BTU air conditioner is your best bet.