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Grid-Tied Solar Electric Systems

The information on this page refers specifcally to solar electric systems used in the Province of Ontario. There may be other provinces and locations where the information and specifics also apply.

In Ontario, at this time - October 2016 - there is a program called the F.I.T. or Feed In Tariff Program. This program pays those who generate and sell electricity from specifically approved, alternative electrical generating technologies, a premium for that electricity. The program began in 2009 and will end 2017. For these technologies to work, and to receive compensation from the IESO, they must be connected to the electrical grid. For solar electric (PV) systems, this requires a Grid-Tied inverter system.

There are two different ways to connect a Grid-Tied system to the grid. In Parallel and in Series.

Solar electric parallel grid tied system

 PV Microfit series connection

There are other ways to have grid-tied solar PV systems - specifically "Net-metered" and "Self-consumption" connections.

Net metered system deliver electricity directly to the load centre of the building they are connected to. Electricity is used by the building in place of electricity from the grid. If the solar system cannot provide enough electricity, additional power is pulled from the grid. If the solar system is generating more than is needed, the surplus electricity is pushed back onto the grid. Net metered systems derive their name from the fact that the electricity meter on the grid will only display the "net" amount of electricity used from the grid. In Ontario at this time (October 2016) utilities will not allow a surplus of electricity from a net metered system to be carried forward for more than 11 months. If there is a surplus it will be zeroed-out, so there is no financial benefit to oversizing a net-metered system.

Most net metered PV systems essentially use their grid connection as if it were a large battery. When there is a surplus of electricity being generate it is "stored" on the grid. However, if the grid goes down and there are no actual batteries connected to the net-metered system, the PV system normally cannot provide power to the building even if it is sunny. By adding batteries and using the right type of inverter, one with a battery controller and a transfer switch, a net-metered system can provide emergency power during grid outages.

Self-consumption PV systems are very similar to net-metered systems with batteries. Self-consumption systems do not push any power on the grid - even though the building is connected to the grid. The power generated is either used by the building or stored in batteries in the building, to be used later. Electricity is normally only pulled from the grid when the PV system or the batteries can no longer supply the electrical demands of the building.

Below are illustrations of net-metered and self-consumption systems.

Net-metered and Self-consumption PV systems