By Tim McLaughlin

BOSTON, Jan 31 (Reuters) - U.S. grid operators are asking regulators for more time to meet a federal order to upgrade existing transmission lines with equipment that can boost their capacity up to 40%, according to a Reuters review of regulatory documents.

The delays represent a potentially years-long setback for efforts to reinforce the nation’s rickety power infrastructure, at a time newly sworn-in President Donald Trump has declared a national energy emergency over soaring U.S. electricity demand from data centers.

The Federal Energy Regulatory Commission in late 2021 had ordered all six major regional grid operators outside of Texas to establish systems that regularly update the capacity ratings on transmission lines, based on weather conditions, by a deadline of July 2025.

High-voltage transmission lines currently rely mainly on static settings that do not factor in real-time temperature drops or cooling breezes that could boost their capacity, meaning less power is often delivered than could be.

Meeting the FERC order requires technology that factors in hourly power line temperatures.

All six regional grid operators, however, have indicated they will not meet the July deadline, according to the Reuters survey.

Some, including the Midcontinent Independent System Operator (MISO), which oversees the wholesale electricity market in 15 states, cited a lack of available software vendors needed to accomplish the work.

MISO told Reuters on Thursday it plans to file a deadline extension with FERC in March, but has not determined how long of an extension it would need.

California's CAISO, whose members are now embroiled in probes and lawsuits relating to devastating wildfires in Los Angeles, told FERC this week it may need until late 2027 to fully implement the agency’s order.

“Getting this done by the July 2025 time frame is too large an effort for us and our participating transmission owners,” Andrew Ulmer, a lawyer for CAISO, said last month during a meeting with stakeholders, when explaining the rationale for a deadline extension.

PJM, which operates in 13 states that include the southern and eastern part of the country, told Reuters it plans to discuss an extension to the FERC deadline during a meeting with transmission owners next week.

The Southwest Power Pool, whose territory extends from North Dakota to Louisiana, told stakeholders earlier this month it would seek an extension for as late as December 2026.

In early 2024, FERC approved a deadline reprieve for New York's grid operator that could extend into late 2028.

New England's grid operator, ISO New England, told Reuters it plans to request a deadline extension in the fourth quarter, but did not say how long it would need.

The delays are emblematic of decades of underinvestment in the U.S. electric grid, said Julia Selker, executive director of WATT Coalition, an advocacy group for more grid technology.

“You need utilities clamoring for this technology to get the regional grid operators moving,” Selker said.

Trump described the electric grid as “increasingly unreliable” in a Jan. 20 National Energy Emergency declaration, which is intended to help him fast-track permitting for new energy infrastructure projects.

FERC told Reuters it is reviewing the president's executive orders and whether they will factor into decisions on deadline extensions.

The White House did not respond to a message seeking comment.

Transmission line congestion cost U.S. electric customers an estimated $11.5 billion in 2023, according to a report from Grid Strategies, a power sector consulting firm.

It has been a major obstacle for new power generation projects, which require transmission capacity to access markets.

Utilities that have already installed sensors based on the FERC order have seen some benefits.

For example, during 2022’s Winter Storm Elliott that knocked out power for more than 1.5 million homes and businesses across the U.S., PPL Corp's PPL.N power lines with advanced sensors boosted their capacity beyond standard settings, which PJM said was critical in avoiding rotating power outages.

(Reporting By Tim McLaughlinEditing by Marguerita Choy)

((tim.mclaughlin@thomsonreuters.com; +1 617-856-4409; Reuters Messaging: Tim.McLaughlin.thomsonreuters.com@reuters.net))