SunEdison Inc. filed for bankruptcy protection after a two-year, $3.1 billion acquisition binge that drove its debt to unmanageable levels and sent investors running for the exits.

The clean-power giant listed $16.1 billion of debt in Chapter 11 filings Thursday in Manhattan federal court, making it the biggest U.S. bankruptcy in more than a year. While the buying spree ultimately did SunEdison in, the bankruptcy comes as energy companies of all sorts are succumbing to a slump in prices.

The company's business model—building clean energy plants around the world and then spinning them off to publicly held companies it controls—may also complicate its reorganization effort. While two of its best known companies, TerraForm Power Inc. and TerraForm Global Inc., are not part of the bankruptcy, SunEdison acknowledged responsibility for some of their debt in court papers.