Moody's on Dec. 11 downgraded Alliant Energy Corp. and utility subsidiary Wisconsin Power and Light Co.

Alliant's senior unsecured rating was downgraded to Baa2 from Baa1, and Wisconsin Power and Light's, or WPL's, rating was downgraded to A3 from A2.

"Alliant and WPL are exhibiting weaker financial profiles over the next few years because high capital expenditures will primarily be financed with debt," Moody's analyst Nana Hamilton said in a report.

Moody's also downgraded WPL's short-term rating for commercial paper to P-2 from P-1, while it affirmed the ratings of Alliant utility subsidiary Interstate Power & Light Co.

"IPL's capital spending will decline going forward and thanks to credit supportive regulatory developments in Iowa, key financial credit ratios will improve to the high-teens range," Hamilton said.

The rating outlooks for Alliant and both of its subsidiaries were revised to stable from negative.