PJM's Surplus Interconnection Service Reforms Advance Grid Capacity Sharing

PJM's updated rules for sharing surplus grid capacity could lower energy costs for 130M+ North Americans by better utilizing existing infrastructure.

PJM reformed its Surplus Interconnection Service (SIS) rules in early 2025, enabling more efficient use of regional grid capacity. Since 2023, PJM has approved two SIS projects and received eight applications, while MISO and SPP are studying 14.8 GW and 14.3 GW of potential projects respectively as of June 2026. PacifiCorp is reviewing 5.2 GW across five Western states. Forty-four SIS projects came online in MISO since 2024, and twenty-two started in SPP since 2024. The reforms aim to reduce regional energy imbalances by allowing surplus capacity to flow where needed, potentially lowering costs for 130 million people across North America.

The mechanism hinges on redirecting unused grid capacity—currently constrained by rules that prevent battery systems from accessing interconnection rights. By permitting hybrid resources to participate in markets as separate entities, PJM seeks to unlock thermal and renewable facilities that could support up to 150 GW of solar, wind, and storage capacity. This addresses the current bottleneck where battery systems cannot access existing capacity rights due to co-located resource limitations.

This progress moves energy affordability closer to universal access by reducing regional price disparities. However, the capacity auction shortfalls have increased from 6.5 GW (2027/28) to 6.8 GW (2028/29), signaling ongoing challenges in scaling the system. What matters next is whether PJM resolves the battery access constraint while maintaining the pace of project deployment. The source notes PJM does not publicly release SIS request details beyond periodic updates to its Interconnection Process Subcommittee.

Source: Utility Dive