A multifunction inverter is an electrical inverter than can operate as either a stand-alone inverter or a synchronous inverter. In a typical installation, a multifunction inverter is connected to a battery bank, the utility power lines, a standby generator, and the house load center. When batteries are in a charged condition, the inverter supplies AC power to the house from the batteries. If the batteries become discharged, the inverter supplies the house loads from the utility lines, while charging the batteries. If the batteries become fully charged by another power source, such as photovoltaic modules or a wind or hydroelectric generator, excess power may be sold back to the utility. If utility power fails, the inverter can still operate, supplying critical loads. If a standby generator is started, it can also supply power to loads. The inverter will synchronize to the generator and allow loads to be powered that are too large for either the generator or inverter to supply alone.