There are two types of electricity:
- Alternating current (AC) electricity, in which the direction of the electric current changes 50 or 60 times per second. AC electricity is provided by the national electricity grid, diesel generators and inverters.
- Direct current (DC) electricity, in which the direction of the electric current does not change. DC electricity is delivered by batteries and photovoltaic modules.
An inverter converters DC electricity to AC electricity.
Most solar electric systems have inverters, either to convert DC electricity from the PV modules into AC electricity, or to convert DC electricity from batteries into AC electricity.
Electric symbol for an inverter with symbol for AC (top left); symbol for DC (bottom right).
There are several different types of inverters used in solar electric systems. Larger systems will often have more than one inverter, sometimes even different types. The type(s) of inverters used will mainly depend on whether a system is grid-connected or off-grid. Modern, good quality inverters will have average efficiencies of more than 90%.