Entergy New Orleans is trying to rush approval of a new power plant at Michoud in New Orleans East while failing to justify the size of the project, City Council members and their advisers said as they blasted the utility Thursday.

The council’s Utility, Cable, Telecommunications and Technology Committee demanded the utility hand over data and documentation justifying the $216 million project within 30 days amid questions about whether the plant, which would be capable of generating 250 megawatts, is the best way to meet the city’s need for additional electrical power.

The approval process for the plant, which would replace two aging units at the site that were deactivated this month, has “gone off the rails,” said Clint Vince, the council’s principal adviser on energy regulation.

The dispute focuses on how Entergy should replace the power generated by those two units.

Council members, who regulate the utility and would need to sign off on building the plant, and renewable energy advocates argue that Entergy’s plans do not focus enough on energy efficiency and alternatives such as wind and solar power.

Entergy has argued those options are too expensive, but Vince and others said the utility has not provided adequate information to prove its case.

The process should have provided enough information so council members could weigh options and “we could say, ‘Maybe it’s a little bit more (expensive), but it’s so good for the city and the world that we’re going to do it,’ ” Councilwoman Stacy Head said.

Councilwoman Susan Guidry said the utility had not yet made the case for the new plant. “I want to be convinced that we need a plant at all,” she said.

The size of the plant matters not only for the city’s current power needs but also for those in the future, Vince said. The full capacity of the new plant wouldn’t be needed until 2030, and having that much capacity on hand could keep Entergy from turning to renewables even if, as expected, they get cheaper in the coming years, he said.

Vince, who described the city’s past relationship with Entergy as largely positive, said the current situation leaves the council at a “serious regulatory impasse.”

Among the issues he raised was Entergy’s alleged failure to provide data comparing the costs of using fossil fuels versus renewables, to justify the size of the plant or to properly explain how it grew from 194 megawatts to the currently proposed 250.

“The process appears to be result-driven and has not provided adequate information,” Vince said.

Others, including Councilman Jason Williams, said the utility has not seriously engaged with advocates who are involved in the process.

“We are going to make sure that everybody’s heard and that we come out with a resolution that fits this community’s needs,” Williams said. “The only way we can do that is if at those community meetings we don’t just retreat to corners.”

Entergy hopes to get approval to move forward with the project by early next year. Gary Huntley, the company’s vice president of regulatory affairs, said it is planning to address the concerns raised through the process.

“I think that’s where we’re going to have a very substantive discussion and go through all the vetting that I think your advisers mentioned earlier,” Huntley said.

Follow Jeff Adelson on Twitter, @jadelson.​