Grid-tied systems are the most common type of solar PV system. Grid-tied systems are connected to the electrical grid, and allow residents of a building to use solar energy as well as electricity from the grid. Grid-tied systems do not need to produce 100% of the electricty demand for a home or business. When there is no demand for energy, the solar panels send excess electricity back out into the grid for use elsewhere. When a home or business is using energy, but the solar panels aren't producing enough energy (at night, or on a stormy day), electricity from the grid supplements or replaces electricity from the panels. Owners of a grid-tied system complete a net metering agreement with their utility incase available. This agreement allows utility customers to receive credit for the excess energy they generate, typically credited as a kilowatt-hour credit on the next month's bill. Net metering policies and agreements are different for each utility and is governed by state policies. Living with a grid-tied solar PV system is no different than living with utility electricity and DG use, except that some or all of the electricity you use comes from the sun. Grid-tied systems do not provide protection from power outages. When the electrical grid fails, grid-tied systems will not continue to operate. This allows utility employees to fix the power lines safely without wasting time identifying solar energy systems that are still feeding electricity into the power lines. This security feature is called islanding.
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