Interconnection Standards

Summary

DC's interconnection rules apply to all distributed generation systems of 20 megawatts (MW) or smaller that are operated in parallel with the electric distribution system and are not subject to the interconnection requirements of the PJM Interconnection.

The interconnection rules set four levels of review for interconnection requests. A project must meet all of the requirements of a given classification in order to be eligible for that level of expedited review. The level of review required is generally based on system capacity, whether system components are certified, and the type of distribution circuit to which a facility will be connected. The basic definitions* for each level are as follows:

• Level 1: Certified, inverter-based systems with a capacity rating of 20 kilowatts (kW) or less.
• Level 2: Certified systems with a capacity of 1-5 MW or less, depending on line capacity.
• Level 3: Only applies to systems that will not export power to the grid. Systems must have a capacity rating of 20 MW or less.
• Level 4: Systems with a capacity of 20 MW or less that do not meet the criteria for inclusion in a lower tier.

The interconnection regulations generally use IEEE 1547 as a technical standard for evaluation of all levels of interconnection. Systems are considered to be lab-certified if the components have been evaluated by a nationally recognized testing laboratory as compliant with UL 1741 (inverters) and IEEE 1547.1. The rules specify the technical screens which may be applied to applications at each level of review and time limits for different stages of the evaluation process. Generally speaking, higher level applications are subject to more intensive screening and longer time limits.

There are no fees for Level 1 interconnections.

Facilities interconnecting after January 1, 2022 must include advanced inverters, if commercially available.

History
The PSC adopted net-metering rules in February 2005 for residential and commercial electric customers with renewable-energy systems, fuel cells, cogeneration and microturbines up to 100 kilowatts (kW) in capacity. In January 2007 the PSC approved a net-metering tariff filed by Pepco -- the only electric distribution company that serves the District -- which also contained certain technical standards for net metered facilities. Prior to this, in 2003, Pepco had filed an interconnection tariff to address larger qualifying facilities (QFs) under PURPA.

In July 2006 the District of Columbia Public Service Commission (PSC) initiated a formal inquiry into the development of uniform interconnection procedures for on-site distributed generation systems. The PSC subsequently concluded that an interconnection standard was feasible and continued with the rule making process, culminating with the adoption of final interconnection regulations in February 2009 (DC PSC Order No. 15182).

The PSC made changes to interconnection rules in 2019 and 2021.

*The definitions here cover several important classification criteria; however, interested parties should consult the actual rule for more precise definitions and additional restrictions.