Metering configurations for Rooftop Solar Power Plants

  • There are two common types of metering arrangements available for solar PV Installations.
    • net-metering
    • gross metering
  • Selection of the metering configuration that best suits the consumer depends upon on the purpose of solar PV system installation and state regulations.

General utility metering arrangement

A general utility metering arrangement caters electricity supplied through the utility grid to a consumer via power distribution lines. The utility installs an energy meter to monitor and record the consumption i.e. the amount of electricity imported by the consumer.

Net metering

Net metering is a utility billing mechanism that allows the consumer to export the surplus solar generation from grid-connected solar PV system into the utility grid. This arrangement changes the consumer interaction with the utility from a one-way relationship to a two-way relationship. With net metering, the consumer not only imports the electricity from the grid but also gains the ability to export the electricity to the grid which is recorded by a bi-directional energy meter installed by the utility.

A solar PV system can often generate more electricity than one consumes during daylight hours. This combination of high output and low usage results in surplus power.

With net metering, the consumer can export this surplus electricity during daytime to the utility grid and consume the electricity when solar system is not generating. Therefore, with the net-metering arrangement, a consumer is only billed for the “net” energy used, i.e. the difference between the energy produced by the solar PV power system and the energy consumed over the billing period. The billing arrangements can be different depending upon a state’s net-metering policy.

Gross metering

Gross metering is a utility arrangement that allows the consumer to export the total number of units generated by the grid-connected solar PV power plant, into the utility grid. The consumer is paid a feed-in tariff (FiT) for the electricity exported which is accounted by a unidirectional gross meter installed by the utility.

With gross metering, the consumer has to pay the electricity distribution company at retail supply tariff for the electricity consumed from the grid.

The consumer is not allowed to use the generated solar power (even partial) for his own consumption and all generated units (kWh) is required to be exported. Such an arrangement is usually a long-term contract between the consumer and the electricity distribution company which is executed in the form of Power Purchase Agreement (PPA). The (FiT) can be different depending up a state’s regulations.

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