If it’s time for a new window air conditioner, but you don’t know what size you need, this chart will be helpful. Air conditioners are rated by BTUs and their cooling capacity is directly related to the number attached to this BTU symbol. The larger the BTUs, the greater the cooling capacity.
Another factor is physical size. The size of the window air conditioner is directly related to the number of BTUs, let me explain. You see, small window air conditioners have smaller BTU ratings. The larger the BTU cooling capacity, the larger the window air conditioner.
The next thing to consider when sizing a window air conditioner is the power availability near the window that you’re going to install the unit. Window air conditioners come in both 120- and 240-volt models. Each requires a different electrical outlet, so be sure to check that out in advance of purchasing the unit or you may need to rewire and outlet for the unit.
Also consider the actual window opening that the unit will be placed in. To do this, open the bottom window and measure the height and width of the window opening. This is the maximum opening that the window air conditioner can fit.
The table below lists the square footage of the room and the required BTUs needed to sufficiently cool the room. This gives an indication of the size unit that will run the most efficiently, without overworking the air conditioner on those hot days.