PJM Interconnection (United States)

What it is

PJM Interconnection LLC is a US regional transmission organization (RTO) regulated by the Federal Energy Regulatory Commission (FERC). It coordinates the movement of wholesale electricity across all or parts of 13 states, Delaware, Illinois, Indiana, Kentucky, Maryland, Michigan, New Jersey, North Carolina, Ohio, Pennsylvania, Tennessee, Virginia, and West Virginia, plus the District of Columbia. The service territory spans roughly 400,000 square miles and serves more than 67 million people, making PJM the largest grid operator in North America. PJM does not own generation or transmission assets; it dispatches power from member generators and runs the competitive wholesale markets through which electricity is bought and sold. As of early 2026, the grid holds roughly 182 GW of installed generating capacity across 88,333 miles of transmission lines. More than 1,000 companies are PJM members, including utilities, independent power producers, retail electricity suppliers, and large industrial customers.

History

Three US utilities, Public Service Electric and Gas, Philadelphia Electric, and Pennsylvania Power and Light, formed the Pennsylvania-New Jersey Interconnection in 1927, the world's first continuing power pool, to share generating reserves across state lines. Baltimore Gas and Electric and General Public Utilities joined in 1956, prompting the rename to Pennsylvania-New Jersey-Maryland Interconnection (PJM). PJM deployed the first online computer for generation control in 1962 and launched a digital energy management system for real-time transmission monitoring in 1968.

Deregulation reshaped the organization in the late 1990s. PJM opened the US's first bid-based wholesale electricity market on 1 April 1997 and, later that year, received FERC approval as the nation's first independent system operator (ISO). In 2002, FERC formally certified PJM as a fully functioning RTO, giving it authority over grid reliability and wholesale market design. Between 2002 and 2013, a series of utility integrations brought in service territories in Illinois, Ohio, Indiana, West Virginia, North Carolina, and Kentucky, roughly tripling the footprint.

Current state

As of mid-2026, PJM is under acute supply pressure. Its December 2025 capacity auction for the 2027/2028 delivery year procured 134,479 MW, clearing at US$333.44/MW-day for a total of US$16.4 billion, but fell 6,623 MW short of the reliability requirement, the first time PJM failed to clear the full target. Peak demand is projected to grow 32 GW by 2030, with roughly 30 GW attributed to data centers. Wholesale power averaged US$136.53/MWh in Q1 2026, up from US$77.78 a year earlier.

In May 2026, the US Department of Energy invoked Section 202(c) of the Federal Power Act to authorise PJM to curtail large industrial loads, including data centers operating backup generators, before ordered rolling blackouts, as covered in 美国最大电网濒临供应缺口，能源部批准PJM限制数据中心用电. Capacity costs, the subject of 数据中心推动PJM电价飙升63%，反弹情绪持续升温, have reached a record, and 23 US states had by May 2026 adopted or proposed large-load tariffs to shift those costs onto high-consumption customers.

Relationships

PJM operates within the Eastern Interconnection, one of the two main US alternating-current grids, and exchanges power with neighboring operators including MISO, NYISO, and PJE (the Maritimes). FERC is PJM's primary federal regulator, reviewing tariffs and market rules under the Federal Power Act. Monitoring Analytics LLC serves as PJM's independent market monitor, publishing annual State of the Market reports. State public utility commissions in the 13 states govern retail rates but do not set PJM wholesale market rules. Hyperscalers including Microsoft, Amazon Web Services, and Google are large direct participants in PJM markets through long-term power purchase agreements and interconnection queue filings.

What to watch

• Whether summer 2026 demand peaks trigger actual load curtailments under the May 2026 DOE emergency order.
• The 2028/2029 capacity auction result and whether new generation supply closes the 6,623 MW reliability gap before the projected 2027 shortfall onset.
• FERC rulemaking on large-load tariff structures that would place capacity costs on data centers rather than spreading them across residential ratepayers.
• State-level grid reliability legislation in Virginia, Maryland, and Pennsylvania responding to the volume of new data-center interconnection requests in PJM's queue.