If a major coal plant goes down and no one notices, can it impact reliability?

Dive Brief:

Talen Energy's Colstrip coal generating facility in Montana has been shut down for a month or more, the Billings Gazette reports, due to difficulties meeting emissions standards. Colstrip is one of the largest coal plants in the country.
The outage comes in the midst of a national debate over the necessity of fuel-based power plants and the federal government's consideration of a plan to stem a wave of coal and nuclear plant retirements.
Talen already planned to shutter units 1 and 2 by 2022. Those units were offline for scheduled maintenance, so compliance issues with units 3 and 4 put the entire plant offline.

Dive Insight:

Montana has reduced its coal-fired capacity down to 37% from around 55% in 2015, according to a report this year from the state's Legislative Services Division. The decline in Montana mirrors resource changes across the country, and is part of the reason the White House is discussing plans to halt more power plant retirements.

But it is also why the shutdown of Colstrip, and how little news it generated, is significant. While the older Colstrip units are being phased out, units 3 and 4 were expected to continue operating.

Earlier this summer, President Trump directed Secretary of Energy Rick Perry to stop the closure of coal and nuclear plants, which are often shuttered because they cannot compete with cheaper electricity from natural gas and renewables. A large part of the rationale behind subsidizing these plants, according to the Administration, is national security and the potential vulnerabilities created by an unstable grid.

So what happens if a major coal plant fails?

Apparently, very little. Colstrip — all four units — has been offline for at least a month, according to the Gazette. In that time, the closure has drawn relatively little attention. Opponents of coal say this lack of impact is proof the administration's fears are overwrought.

The Colstrip shutdown also proves that coal plants are not needed to power the area, according to a tweet from Brian Willis, press secretary for Sierra Club's Beyond Coal campaign.

Over and over millionaire coal executives ask us for billions in bailouts or "the lights will go out." In the meantime, one of the largest coal plants in the U.S. shuts down for a month. Lights are on and its cheaper to keep the lights on: https://t.co/7lbq1e3Mz0 #NoCoalBailouts
— Brian Willis (@Bwillisful) July 25, 2018

Whether or not electricity in Montana is cheaper without Colstrip is up for debate. Travis Kavulla, vice chair of the Montana Public Service Commission, tweeted that he expected a difference in electricity prices based on changes in the spot market.

This evening power is trading at $200+/MWh in region vs <$20/MWh Colstrip production cost. So I feel comfortable saying this outage won't actually save people money. https://t.co/TQv9rm5IBT
— Travis Kavulla (@TKavulla) July 25, 2018