NEW YORK, July 30 (Reuters) - An annual power market

auction by the largest U.S. electrical grid operator resulted in

prices more than 800% higher than last year as supply dwindled

and demand increased, the operator said on Tuesday.

PJM Interconnection, which covers parts of 13 states from

Illinois to New Jersey, revealed the results of its 2025 to 2026

capacity auction. Prices for power plants landed at $269.92 per

megawatt-day, compared to $28.92 per megawatt-day for year-ago

auction, the grid operator said in a statement.

"The significantly higher prices in this auction confirm our

concerns that the supply/demand balance is tightening," said PJM

Chief Executive Officer Manu Asthana said. "The market is

sending a price signal that should incent investment in

resources."

The auction secured 135,684 megawatts for the period from

June 1, 2025, through May 31, 2026. The power mix from

generators included 48% gas, 21% nuclear, 18% of coal, 1% of

solar, 1% of wind, 4% of hydro, 5% of demand response and 2%

from other resources, PJM said.

Shares of independent power producers with nuclear fleets,

including Constellation Energy ( CEG ), Vistra ( VST ) and Talen

, jumped in after-hours trading following the auction.

Constellation shares were up about 10% to $185.10, Vistra ( VST )

rose 12% to $77.50 and Talen gained roughly 18%, according to

Refinitiv Eikon data.