Maine Central Maine Power and Versant Power Solar Net Energy Billing Guide

This guide outlines the Net Energy Billing framework in Maine, as it applies to customers of Central Maine Power (CMP) and Versant Power who are considering or operating solar energy systems. While the state statutes define the billing and credit mechanisms, specific technical interconnection procedures, such as Level 1 requirements, disconnect switch mandates, and utility-specific application processes, are governed by separate regulations (like Chapter 324 rules) and utility documentation, which are not detailed in the provided statutory information.

Understanding these billing policies is crucial for any solar installation, as they dictate the financial benefits and operational rules for connecting your distributed generation resource to the grid.

What is Net Energy Billing?

Net energy billing is a foundational practice in Maine for integrating customer-owned generation, such as solar panels, with the electrical grid.

1. Residential Net Energy Billing: This practice bills a customer based on the difference between the kilowatt-hours delivered by the utility and the kilowatt-hours the customer delivers to the utility over a billing period. It also accounts for accumulated unused kilowatt-hour credits from previous billing periods.
2. Commercial and Institutional Net Energy Billing: The Maine Public Utilities Commission establishes a specific net energy billing program for commercial and institutional customers of investor-owned utilities, following similar principles.

Defining a Distributed Generation Resource

For the purpose of net energy billing, a "Distributed generation resource" means an electric generating facility that uses a renewable fuel or technology under section 3210, subsection 2, paragraph B‑3 and is located in the service territory of a transmission and distribution utility in the State. This definition applies to both residential and commercial/institutional contexts.

System Size Limits for Net Energy Billing

Maine statutes set clear limits on the nameplate capacity of systems eligible for net energy billing:

• Residential Systems: The nameplate capacity of a distributed generation resource that may be used for net energy billing must be less than 5 megawatts. An exception exists for municipalities, where the nameplate capacity may be 5 megawatts or more, as long as less than 5 megawatts of metered electricity from the resource is used for net energy billing.
• Commercial and Institutional Systems: The nameplate capacity of a distributed generation resource that may be used for net energy billing under this section must be less than 5 megawatts.

Shared Financial Interest Limitations

For customers with a shared financial interest in a distributed generation resource, specific limits apply, particularly in northern Maine:

• Residential and Commercial/Institutional: The number of eligible customers or meters is limited to 10 for a shared financial interest in a distributed generation resource located in the service territory of an investor-owned transmission and distribution utility located in an area administered by the independent system administrator for northern Maine, unless the commission determines that the utility's billing system can accommodate more than 10 accounts or meters for the purpose of net energy billing.

Key Dates for Net Energy Billing Agreements

Several important dates impact net energy billing agreements:

• Agreement Amendments: An amendment, revision or reissuance of a net energy billing agreement made after June 1, 2025 may not include a delivery period end date that is later than the end date provided for in the agreement that is subject to the amendment, revision or reissuance.
• Commercial Operation Deadlines: For residential distributed generation resources between 1 MW and 5 MW, commercial operation must be reached by December 31, 2024, or by the date specified in the net energy billing agreement with allowable modification.
• Future Agreement Prohibition: After December 31, 2025, the commission may not allow a transmission and distribution utility to enter into a net energy billing agreement with a distributed generation resource that is interconnected or planned to be interconnected to the distribution grid on the utility side of a customer's utility meter. This prohibition applies to both residential and commercial/institutional resources.

Commercial and Institutional Tariff Rates

The tariff rate for commercial and institutional customers participating in net energy billing varies based on system size and the date of application:

• Systems up to 1 MW (or >1MW with specific conditions) until December 31, 2025: The tariff rate for a customer participating in net energy billing with a distributed generation resource described in this paragraph, until December 31, 2025, must equal the standard-offer service rate established under section 3212 that is applicable to the customer receiving the credit plus 75% of the effective transmission and distribution rate for the rate class that includes the smallest commercial customers of the investor-owned transmission and distribution utility.
• Systems not governed by the above paragraph: In 2022, the tariff rate equals the standard-offer service rate established pursuant to section 3212 that was applicable to the rate class of the customer receiving the credit on December 31, 2020 plus 75% of the effective transmission and distribution rate that was in effect on December 31, 2020 for the rate class that includes the smallest commercial customers of the investor-owned transmission and distribution utility. This rate increases by 2.25% on January 1st of each subsequent year, beginning January 1, 2023.
• Systems 3 MW to less than 5 MW, beginning January 1, 2026: The tariff rate must equal the tariff rate calculated under paragraph A‑1 applicable in 2026, and increase by 2.25% on January 1st of each year, beginning January 1, 2027.
• Systems less than 3 MW, beginning January 1, 2026: The tariff rate must equal the tariff rate established by the commission pursuant to paragraph A that was applicable in 2025 to the rate class of the customer receiving the credit, and increase by 2.25% on January 1st of each year, beginning January 1, 2027.

Commercial and Institutional Bill Credits

• Credit Carry Forward: Credits that remain unused at the end of any billing period may be carried forward for up to one year from the end of that billing period.
• Credit Duration: A customer participating in the program who remains eligible to participate in the program must be allowed to receive a bill credit based on the tariff rate for a period of no less than 20 years from the date of first receiving the credit.

Collocation Requirements for Commercial and Institutional Systems

• After December 31, 2023: A distributed generation resource may be used for net energy billing under this section only if the distributed generation resource is collocated with all of the distributed generation resource's net energy billing customers and those customers are subscribed to 100% of the facility's output under this section. This limitation does not apply to a distributed generation resource with a net energy billing agreement that was executed on or before December 31, 2023.

Important Note on Interconnection Details

This article focuses on the Net Energy Billing policy framework as defined by Maine statutes. Specific technical interconnection requirements, such as Level 1 interconnection procedures, mandated disconnect switches, adherence to IEEE 1547 or UL 1741 standards, application fees, or utility-specific rules for Central Maine Power (CMP) and Versant Power, are not detailed within these statutes. For these technical specifics, you must consult the Maine Public Utilities Commission's Chapter 324 interconnection rules and the individual utility's interconnection guides and forms.