The number of watts a 5,000-BTU air conditioner uses depends on the number of amps it has and how many volts an outlet has. Most 5,000-BTU air conditioners use 5 amps, and when plugged into a 110-volt outlet, the unit uses 550 watts.
Window-unit air conditioners typically have a range between 5,000 and 18,000 BTUs. BTU stands for "British Thermal Unit." The more BTUs an air conditioner has, the more powerful it is. Taking the square footage of a room and multiplying it by 35 gives an approximate amount of needed BTUs. Window-unit air conditioners were first made available for sale in 1935 and were designed by engineers from Chrysler Motors.