Definition
An energy storage system (ESS) for net metering purposes is defined as a commercially available technology that is capable of:
- absorbing energy;
- storing it for a period of time; and thereafter
- dispatching the electricity.
The ESS may not be any technology with the ability to produce or generate energy.
Permissible configurations
This page focuses on the configurations of net metering facilities paired with an ESS that are eligible to participate in the net metering program. The table below summarizes the 3 configurations that are allowed to net meter and 1 configuration that is not eligible to net meter. For more information on these configurations, read D.P.U. 17-146-A.
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ESS only charges from net metering facility |
ESS charges from net metering facility and electrical grid |
|
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ESS cannot export to the electrical grid |
eligible to net meter |
eligible to net meter |
|
ESS can export to the electrical grid |
eligible to net meter |
not eligible to net meter |
If a net metering facility paired with an ESS is not eligible to net meter, it may still be able to interconnect to the distribution system grid as a qualifying facility for example.
System of Assurance
A host customer of an existing or new net metering facility paired with an ESS will need to provide information about the energy storage system to their electric company and the Administrator of the System of Assurance of Net Metering Eligibility. If the electric company or the Administrator finds that the paired system does not meet the requirements in D.P.U. 17-146-A, the host customer will not be eligible to net meter and will forfeit its cap allocation.
Inadvertent export
30 seconds is the maximum timeframe unscheduled power can export in non-export configurations.
When a net metering facility paired with an ESS is configured to not export to the electrical grid, power may export for no more than 30 seconds. The customer cannot be compensated for the export of energy to the electrical grid in this situation.
Energy storage and the forward capacity market
Host customers or facility owners hold title to the energy and capacity rights associated with the ESS portion of a net metering facility that is paired with ESS. D.P.U. 17-146-B at 22. All Class II and Class III net metering facilities, whether or not they are paired with an ESS, must meet ISO‑NE rules and requirements to ensure that the net metering facility can participate in the ISO‑NE markets. It is the host customer’s and not the electric company’s responsibility to ensure that the net metering facility portion of a paired system remains eligible to participate in the ISO‑NE markets. For more information on ownership of energy and capacity rights for all net metering facilities read D.P.U. 17-146-B.