Kara Zorn on May 12, 2014 71 Comments Before purchasing a window air conditioner, it is important to note the electrical requirements as window A/C units are typically more powerful than standard household appliances. Do You Have The Best Window AC? Most common voltage ratings for AC units are 115, 125 and 220 volts, and amperage rating can run from 15 to 20 amps. The lower two voltage ratings are common in smaller units, while units with a rating higher than 15,000 BTUs will require a 220-volt circuit. Smaller units with a 115 volt and 15 amp requirement will be able to operate off a standard household outlet. However, larger units that have higher energy requirements need a committed outlet to handle the electrical current required for operation. If you already have a committed outlet for your AC unit, you’ll want to try to select a replacement with the same ratings and plug type to eliminate the need of having a new outlet professionally installed by an electrician. If you’re installing a new unit, take note of the wattage, voltage and plug type indicated. Plug types are listed by their NEMA (National Electrical Manufacturers Association) classification and will often include a picture of the plug receptacle for your reference. Some of the most common examples include: Note: Extension cords can be used when needed but only cords rated specifically for window air conditioners or other similar gauge home appliances should be used. See packaging for certification, voltage and amperage ratings prior to use.