PJM desperately needs grid batteries. Here’s a way it could get some.
PJM Interconnection will reform market rules to ease battery additions at existing power plants and renewable sites, aiming to cut delays and costs while meeting rising electricity demand.
PJM Interconnection, the largest U.S. grid operator serving 13 states, has lagged in adopting surplus interconnection service (SIS) rules that allow existing power plants and renewable sites to add batteries without lengthy delays. The Federal Energy Regulatory Commission mandated grid operators implement SIS to enable batteries to store excess power and inject it during peak demand, such as hot summer afternoons or cold winter mornings. PJM’s congested grid and soaring capacity costs, driven partly by data center demand, have intensified the need for reform, yet only two SIS projects have been approved out of 14 submitted as of November 2025.
PJM’s Market Implementation Committee will consider next steps on November 4, 2025, with a potential plan to seek Federal Energy Regulatory Commission approval by April 2027. The reforms aim to unlock 24 gigawatts of energy storage at existing sites, according to Lawrence Berkeley National Laboratory estimates, while saving developers over $31 billion in interconnection costs and grid upgrades. Projects under SIS could come online within one to two years, far faster than traditional new power plants or battery installations in PJM’s backlogged queues.
Clean energy developers, particularly renewable energy firms, have rapidly adopted SIS to maximize existing grid connections, with 44 gigawatts of historical SIS project requests tracked by mid-2026. About 80% of these requests involve adding batteries to existing solar or wind farms, including projects by NextEra Energy and Great River Energy in North Dakota and proposals in California and Illinois. The Midwest grid operators Midcontinent Independent System Operator and Southwest Power Pool lead in SIS activity, with 14 gigawatts proposed in each territory, compared to just 1 gigawatt in PJM’s region.
The primary barriers to SIS adoption in PJM involve grid impact studies and market rules differentiating old and new resources at the same interconnection point. While PJM addressed grid impact study reforms in early 2025, no new SIS projects have advanced due to unresolved contract modifications required for adding new resources alongside existing ones. Clean energy groups continue to push for comprehensive market rule changes to fully unlock SIS potential.