PJM, MISO, SPP and NYISO joined a chorus of critics last week in warning that the Environmental Protection Agency’s proposed carbon emission rule threatens grid reliability, saying the agency should provide more time to build the generation, transmission and natural gas pipelines needed to comply.

At the same time, officials in New England and elsewhere complained that the EPA’s Clean Power Plan does not give enough credit for carbon emission reductions that have already been accomplished.

The critiques were among more than 1.6 million comments filed with the EPA before a Dec. 1 deadline.

SPP warned of rolling blackouts while NYISO said the plan ignored New York City’s reliance on oil-fired generation. PJM, MISO, NYISO and the ISO/RTO Council called on the agency to add a reliability “safety valve.”

Sen. Lisa Murkowski (R-Alaska), who will likely become chairman of the Senate Energy and Natural Resources Committee under a Republican majority next year, and House Energy and Commerce Committee Chairman Fred Upton (R-Mich.) last month called on the Federal Energy Regulatory Commission to convene a technical conference to address reliability concerns.

Some congressional Republicans have threatened to use oversight hearings and appropriations bills to blunt the rule. But lacking a veto-proof majority, the GOP is unlikely to block President Obama’s signature environmental initiative. (See GOP Election Victories Unlikely to Thwart EPA Carbon Plan.)

The proposed rule would require states to devise plans to cut existing power plant carbon emissions from 2005 levels by 30% by 2030, with intermediate goals along the way.

The EPA signaled in October that the final rule, due in June 2015, may relax the interim targets. (See EPA Signals Flexibility on Interim Carbon Targets, Coal-Gas Shift.)

RTO Insider has a roundup of the comments by RTOs, state officials, utilities, trade groups and environmental organizations:

• MISO, SPP: EPA Plan Threatens Reliability, Needs Longer Compliance Schedule
• NYISO: EPA Plan Threatens Reliability for New York City
• PJM: Emission Rules Should Include Reliability ‘Safety Valve’
• RGGI: ‘Building Blocks’ May Overlook Progress of Early-Action States
• Generators: EPA Interim Goals Unrealistic
• Other Voices: More than 1.6M Comments in Response to Clean Power Plan