Where can it be used?

On-Grid:
Under a feed-in-tariff (FIT) or with net-metering, PV generated electricity is fed into the grid, and a meter is used to meter the amount of electricity provided into the grid. Depending on the FIT or net-metering program, which vary from state to state, PV system owners are being paid for PV power, or have a surplus power account which they can draw from at times of power need beyond the PV power system generation.

Off-Grid:
Self contained PV solutions which generate electric power for immediate use or storage in batteries for later use. "Island solutions" allow you to become completely self-sufficient, truly an energy island on itself.