DERs in the ERCOT Interconnection

Distributed Energy Resources (DERs) are a steadily growing part of the resource mix in ERCOT and across the world. While DERs are not directly connected to the Bulk Power System (BPS), NERC has tracked these developments and convened the System Planning Impacts from DERs Working Group (SPIDERWG) to consider the effects on BPS reliability.

SPIDERWG has been prolific in its development of twelve whitepapers, a technical reference, and six Reliability Guidelines, with the most recent guideline update for Bulk Power System Reliability Perspectives on the Adoption of IEEE 1547-2018 approved on June 11 by NERC’s Reliability and Security Technical Committee. The guideline provides aggregators, regional Transmission Operators, Planning Coordinators, and Distribution Providers with an overview of IEEE 1547-2018, guidance on application to studies, and understanding of BPS impacts. IEEE 1547-2018 is an international standard used by equipment manufacturers for inverter-based resources (IBRs) connected to the distribution system. It preceded IEEE 2800-2022, which applies to transmission-connected IBRs, which was the starting point for NERC’s PRC-029-1 Reliability Standard and ERCOT’s NOGRR245. The revision updates the comparison between these IEEE standards, an important consideration given the concerns with disturbance ride-through capability.

ERCOT’s annual DER report shows 7,230 MW of capacity at the end of 2025, with over six GW of capacity IBR-based solar and battery systems. One area of particular interest is the growth of aggregated DER (ADER) in its pilot program, which has increased rapidly in the last year. ADERs recently reached 241 MW of energy capability, with an additional ancillary services capability of 79 MW for ERCOT Contingency Reserve Service and 48 MW for non-spinning reserves, based on ERCOT’s evaluation. These resources are controlled as if they were a virtual power plant, providing flexibility to operations. Many ADERs are battery IBR-based and IEEE 1547-2018 becomes relevant to aspects of their performance.