Most homes are wired for AC electricity, but most solar panels and small wind
turbines produce DC electricity. Inverters convert direct current (DC)
electricity into alternating current (AC) electricity. Because of this, unless
your solar system runs DC only, an inverter is usually a central component in
both off-grid and grid-tie solar systems. Each type of system requires a
different type of inverter:
In off-grid systems a charge controller sends DC power to a battery bank, then
an inverter converts the DC to AC for the home.
In grid-tie systems with no battery bank, DC power goes straight to the
inverter, and then to the home as AC. Excess AC power is sent "backwards"
through a special two-way net meter, and out to the power grid for others to
use. Your meter runs forward or backwards depending on if you are buying or
selling power at the time.
A hybrid system connects to both a battery bank and the utility grid, letting
you draw or send power from both.