PJM Approved Two of Eight Surplus Interconnection Applications While 150 GW Sits Behind Existing Plants

PJM Interconnection has opened a second attempt at surplus interconnection service. The pathway lets a new generator or battery connect at an existing power plant’s point of interconnection. A developer who takes it skips the study queue. PJM staff floated new rule changes in August 2026. Since 2023 the grid operator has received eight surplus interconnection applications and approved two. Researchers at the University of California, Berkeley sized that idle capacity. It would carry about 150 GW of solar, wind and storage.

The gap between that estimate and two approvals is the story. Surplus interconnection reuses capacity rights a plant already holds. A gas plant that runs at a 15 percent capacity factor leaves most of its interconnection idle. Solar or storage built at the same substation takes the idle share.

Other grid operators are further along

MISO had 14.8 GW of surplus interconnection requests under study as of June 30. The Southwest Power Pool had 14.3 GW. PacifiCorp reviewed 33 projects across five Western states, worth 5.2 GW, as of August 13. Forty-four surplus interconnection projects have come online in MISO and 22 in SPP’s footprint. Since 2024 the MISO projects took one year on average to reach service. The SPP projects took almost two years.

Against those numbers, PJM has eight applications in three years. A first attempt at the process did not draw developers. Staff now propose a different fix. A battery added to a working solar farm would bid into energy and ancillary services markets as its own resource. The pair would still count as one resource in the capacity market.

That split matters. Capacity interconnection rights, not physical wire, decide what a hybrid project sells. PJM’s Market Implementation Committee would write any rule changes.

States have started legislating

Virginia and Indiana passed laws this year that push utilities toward the option. Virginia’s HB 1065 directs Appalachian Power and Dominion Energy Virginia to assess interconnection capacity at existing and planned intermittent generators. The same law orders pilot programs and requests for proposals. Indiana’s SB 240 tells Northern Indiana Public Service Co. and Indiana Michigan Power to study surplus interconnection in their resource plans. From 2030 an Indiana petitioner who wants to build or buy a plant must weigh surplus interconnection first.

The national prize is larger. A 2024 Berkeley working paper found that existing fossil plants could share grid access with about 800 GW of renewables today. That figure reaches roughly 1,000 GW by 2030.

Why It Matters

Developers holding a queue position at PJM should price the surplus route against the wait. The mechanism works where a host plant has idle rights and a willing owner. The approval record points at paperwork, not physics, as the binding constraint. Watch the Market Implementation Committee for the hybrid-resource proposal. If PJM adopts the split-market treatment, storage at existing solar sites becomes the fastest capacity to build in the footprint. If the committee stalls, expect mandates in the Virginia and Indiana style to spread. Legislators in both states already acted once the operator did not.

Critical Perspective

The article reads two approvals as a paperwork failure. The same numbers support a harder reading. Surplus interconnection service is conditional by design. A project that takes it shares a connection the host plant still controls. It gets curtailed whenever that plant runs. In PJM, where capacity revenue rewards firm availability, that is a poor trade. The 150 GW figure measures idle wire, not projects anyone wants to finance.

Where the number comes from matters too. It is a working paper estimate built from capacity factors and satellite imagery, not a queue of applications. The Berkeley authors put the economically viable share at about 106 GW once the loss of Inflation Reduction Act credits is counted. MISO and SPP show the mechanism works, with 44 and 22 projects online. They also show it is slow, at one to two years per project. Eight PJM applications in three years may reflect developers pricing the service correctly rather than missing it.

Sources

• Utility Dive
• Utility Dive
• Utility Dive
• UC Berkeley Goldman School of Public Policy
• Energy Innovation

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