DETROIT (WWJ/AP) – The Michigan Public Service Commission says DTE Energy and Consumers Energy will have to implement recommendations to prevent widespread and lengthy power outages, like the one last winter that left over 650,000 homes and businesses without service.

The Commission is requiring that both utility companies trim tree branches and consider conducting an audit to determine if staffing levels are adequate.

READ MORE: Detroit Offers Walk-In Vaccinations At Locations, Appointments Still Encouraged

The state Public Service Commission, in concluding an investigation into the December outages, said Friday that it was “unacceptable” for Jackson-based Consumers Energy to spend $16 million less trimming trees in 2013 than had been approved by regulators, the lowest amount since 2008. It said Michigan’s other major utility, DTE Energy, had shown a “strong commitment” to keeping up with tree trimming.

The panel said it will work with Consumers Energy, Detroit-based DTE Energy and local governments to expand successful pilot programs and to pass ordinances addressing hazardous trees located outside the utilities’ rights of way. It also encouraged the adoption of special fees so towns can move some lines underground or trim trees outside utilities’ planned maintenance schedules.

MSPC Chairman John Quackenbush said the large utilities responded appropriately in many ways, but “there are opportunities for improvement.” The commission’s staff said tree maintenance is the most effective way to avoid outages and to limit their duration.

The pre-Christmas ice storm knocked out or disrupted service to roughly 650,000 Consumers Energy and DTE customers statewide. Scores of tree branches broke and fell from the weight of ice during the storm.

Among regulators’ findings:

— Consumers Energy should have called for more help from in-state and out-of-state crews before the storm arrived and earlier in the process of restoring electricity.

— Both utilities must communicate more with customers about the importance of tree removal.

— Customers trying to reach their utility encountered too many blocked calls or had to wait too long. Consumers Energy specifically was ordered to report by Aug. 15 on improvements to handle increased call volumes.

READ MORE: Drive To Repeal Law Gov. Whitmer Used In Pandemic Clears Hurdle

— The utilities and the AFL-CIO should meet to consider the union’s recommendation for an audit on the adequacy of staffing levels.

— The commission will study the feasibility of making automatic an existing $25 bill credit for customers who go without power at least five days.

— The companies should try to speed up their grid and line upgrades to minimize the frequency of outages.

Regulators will report by Oct. 1 on improvements made by the utilities.

Consumers Energy spokesman Dan Bishop said the “catastrophic” storm was among the largest in the company’s 127-year history.

“This report is part of an ongoing dialogue Consumers Energy is having with the MPSC and its staff regarding areas of opportunity for future storm responses and electric system investments,” he said in a statement. “We welcome these open lines of communication and are committed to working with the Commission and staff on these important issues.”

DTE spokesman Alejandro Bodipo-Memba said the utility was satisfied with the findings and pledged to make improvements.

“We also appreciate the Commission’s actions to work on addressing the recurring issues of trees outside our easements causing power outages,” he said.

TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2014 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.

MORE NEWS: Chief Craig: Police Shooting Suspect Was Grieving, Possibly Intoxicated