Interconnection Standards

Note: Public Utilities Commission Rule 5.500 was effectively amended on March 1, 2024, via Docket No. 19-0856-Rule.

Interconnection rules for all net-metering systems are applied by Rule 5.500. Vermont requires electric utilities to offer net metering to all customers with solar photovoltaic (PV) systems, wind energy systems, fuel cells, or biomass energy systems, among others. The maximum system capacity for net-metered systems is 500 kW. CHP systems that use a non-renewable fuel are limited to 20 kW and must meet an efficiency standard. For schools and school district customers, the capacity limit is 1 MW (also applies to aggregate capacity).

Rule 5.500 applies to all proposed interconnections of projects in the state that are not lawfully subject to ISO-New England interconnection rules or any successor rules approved by FERC. Interconnection rules also apply to energy storage projects, including standalone devices and projects combined with other generation resources. All projects that are required to submit an interconnection application under PUC 5.500 must provide certification information, inverter settings information, and if interconnecting energy storage, proposed use cases for storage systems. 

Net-Metered Systems

For net-metered systems with a capacity of up to 15 kW, a net-metering registration form constitutes an interconnection application under PUC Rule 5.500; and the electric companies’ interconnection application review is governed by Rule 5.500. For net-metered systems that have a capacity that is greater than 15 kW, interconnection approval must be granted by the electric company before submitting a registration form.

Interconnection Documentation and Fees

Unless otherwise specified, projects whether net-metered or not, with a capacity of up to 150 kW, greater than 150 kW, or otherwise approved by the Public Utilities Commission must complete an interconnection application. For projects with a capacity of up to 150 kW, an application fee may have to be submitted if required by the utility. As for projects sized greater than 150 kW (including a combination of a generation resource and energy storage system), an application fee of $600 (or the amount specified by the utility), a site plan, site control documentation, and an electrical one-line diagram approved by a licensed professional engineer must be provided.

A Pre-Application Report is optional and may be requested by the interconnector. Requests include a fee of $300 (or the amount specified by the utility). However, a Pre-Application Report request is not placed in the interconnection queue.

Varying procedures exist for projects with a capacity of 500 kW or less and projects with a capacity greater than 500 kW. View PUC Rule 5.500 (LINK to Doc.) for more information.

Study Requirements

A Feasibility Study may be required by a utility, and include the following project information: initial identification of any instances where the short-circuit capability limits of any protective that will be exceeded as a result of the project; instances of thermal overload or voltage limit violations on transmission and distribution systems due to the project; an initial review of islanding, grounding requirements, and system protections; and what the affected utilities are. Within 21 days, those requesting to interconnect and remain in the affected utility’s interconnection queue must submit an executed Feasibility Study agreement and a deposit of the lesser of 50% of estimated study costs or $1,000. A System Impact Study and Facilities Study must also be submitted within 21 days and 30 days, respectively, in addition to deposits equal to the studies’ estimated cost.

System Requirements

A manual external disconnect switch is required. Systems must comply with an array of standards, including IEEE 1547 and UL 1741. Any equipment package will be considered certified for interconnection if it has been submitted, tested, and listed by a nationally recognized testing and certification laboratory or approved by the U.S. Department of Energy.