Nov 26 (Reuters) - Constellation Energy ( CEG ) has

called on the nation's largest grid operator to include in its

tariff rules guidance for interconnected electricity suppliers

to follow when supplying to data centers located next to power

plants.

In a complaint filed against PJM Interconnection with the

Federal Energy Regulatory Commission on Friday, Constellation

alleged that some local utilities are using the lack of such

rules to thwart competition from power generators by opposing

the so-called co-located data centers.

The federal regulator earlier in November had rejected an

agreement to increase the power capacity of a data center

connected directly to a nuclear plant in Pennsylvania, citing

risks to grid reliability and a rise in costs for consumers.

Constellation, which is the largest operator of U.S. nuclear

power plants, had backed Talen Energy ( TLN ) in that regulatory

battle.

Connecting large data centers directly with power plants has

emerged as a major priority for Big Tech's plans to quickly

access large amounts of power for its AI expansion instead of

waiting for years to connect to the grid.

Constellation also said utility firm Exelon ( EXC ), its

former parent, refusing to finish interconnection work at the

LaSalle nuclear plant to support co-location of a data center

could add $15 million to $19 million in costs.

PJM, Constellation and Exelon ( EXC ) did not immediately respond to

requests for comment.

A time-consuming complaint would prove to be negative for

the power companies, Jefferies analysts said in a note.