But collectively, the IRPs provide a unique window into where power companies think the nation's electricity mix is headed. Among the trends: Electric vehicles may have little influence on power demand in the next decade; competition between natural gas and renewables is on the upswing; and battery storage could become less costly. In some locations, coal plants may shutter faster than expected.

"IRPs are very important. They're identifying utilities' preferred plans to meet their capacity needs over the long term," said Coley Girouard, who follows state planning processes for Advanced Energy Economy.

"We've seen IRPs change recently. In the past, they've focused just on traditional baseload resources and supply-side resources," he said.

The IRPs themselves don't grant authority to build or retire power plants or raise rates. Those decisions are made separately in rate cases and other regulatory proceedings.

What many of the plans do is highlight an accelerating transition to cleaner, more flexible energy resources. They also expose tensions created by that shift, especially in states with new 100% clean energy targets and in those phasing out their coal fleets.

"IRPs are working to identify the best other resources to still meet these capacity needs," such as rooftop solar, battery storage and other distributed energy resources, Girouard said.

Read the entire E&E story here to see all 5 trends....