An inverter on a utility-scale PV installation

An inverter, sometimes called a power inverter, is an electronic device that converts direct current (DC) power to alternating current (AC) power. To do so, it must change the current’s direction many times per second to attain the desired AC frequency. This process is called inverting the current.

Inverters are used to convert the output of a DC power source (such as a battery, photovoltaic cell, or fuel cell) to AC power for use by an AC appliance or to inject the power into the grid. Inverters also commonly include a transformer component to increase voltage to the desired voltage. Inverters can be used to convert outputs of variable-speed wind turbines, which have a fluctuating frequency, to a standard 60 Hz and to interconnect microturbines whose spinning speed is too fast to directly synchronize to the grid.  

An inverter used to convert DC power output by a photovoltaic (PV) panel to AC power used by the grid

A power inverter can be entirely electronic or may be a combination of mechanical equipment and electronic circuitry. Electronic inverters are most common since they are better able to create a clean wave that matches the power on the AC grid. They operate by rapidly switching electronic circuits. Modern electronic inverters use switching techniques that create a voltage curve that is practically indistinguishable from the ideal sine wave form desired on the power grid.

DC power is converted to AC power by an inverter