The Mergent Public Utility Manual And News Reports provides financial profiles of public utility companies. The Manual is available in print and online through Mergent's Special Library Service subscription. Profiles for some utilities are published in the Mergent Municipal and Government Manual And News Reports.
The Energy Information Administration and the Federal Energy Regulatory Commission both provide financial and statistical data on U.S. electric utilities.
Decisions and Orders from state public utility commissions are published in Public Utilities Reports (by Public Utilities Fortnightly). You can search and KeyCite Public Utilities Reports on Westlaw (PUR) until August 2014; after that the will be on Lexis.