What Size Power Inverter Do I Need to Run a Portable Air Conditioner?

How a Power Inverter Works

• A power inverter uses electronic components -- such as a microprocessor or heavy-duty transistor set -- to oscillate DC power. This oscillation, when applied across an electrical transformer, can be used as an AC signal.

Power Inverter Wattage Ratings

• Each power inverter is rated as to how much power can pass through the inverter during continuous operation. This rating may be called the "continuous watts" or "continuous load" rating.

  Most power inverters also have a "surge watts" or "VA" rating. The "surge watts" rating is a measure of how much power may pass through the inverter for a short time without damaging the inverter. Some electrical devices contain inductors or electric motors and require more power at start-up than the devices require for continuous operation. Since these electrical loads require more power at start-up, it is important to choose a power inverter that can handle these extra load requirements for a short period of time.

Calculating Device Power

• Before attempting to connect an air conditioner to a power inverter, it is important to know how much power the air conditioner will draw. Many portable air conditioners operate on household voltage, which is approximately 120 volts AC in North America. Watt's Law explains that electrical power may be calculated by multiplying voltage by electrical current. Therefore, if an air conditioner draws a maximum of 7 amps during operation, the power rating would be 840 watts (120 volts x 7 amps).

What Size Inverter to Use

• For best results, choose a power inverter that has a continuous load rating equal to or greater than the maximum power rating of the air conditioner. For example, the air conditioner listed above should be plugged into a power inverter with a continuous load rating of 840 watts or more.