The Mergent Public Utilities manual provides financial profiles of public utility companies; profiles for some utilities are published in the Mergent Municipal and Government Manual. Mergent manuals are available in pint and online.
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). There is a comparable database of public utilities decisions on Lexis.