Wells Fargo Securities LLC on Dec. 18 downgraded several utilities, while raising its rating on CMS Energy Corp.

The firm lowered its rating on shares of Alliant Energy Corp. and PG&E Corp. to "market perform" from "outperform," along with lowering the rating of gas utility Northwest Natural Gas Co. to "underperform" from "market perform."

"These ratings actions primarily reflect valuation considerations and do not reflect concerns with the fundamental outlooks," Wells Fargo analysts wrote in the report. "In addition, after much consideration we are moving to the sidelines on California utility [PG&E] due to the uncertainty around potential shareholder liabilities in the wake of the devastating wildfires in Northern California."

Separately, the firm raised its rating on CMS Energy to "outperform" from "market perform."

"We view CMS as a best-in-class utility," the analysts wrote. "Over the last decade, management has implemented and executed on an attractive regulated rate base growth strategy with an emphasis on customer rates (and cost discipline) that is fairly unique to the utility industry."