An inverter is a power-conversion device that converts D.C. (battery) power to A.C. power. They are a convenient means of powering A.C. appliances from D.C. systems. Inverters are commonly available in the 200-watt to 3000-watt range. Modern mobile systems use only an inverter for A.C. power requirements. One of the biggest advantages of an inverter is that A.C. power is available on-demand without needing to start an engine.