XCEL ENERGY INC.

Electricity customers: 3.4 million

Territory: Minnesota, North Dakota, South Dakota, Wisconsin, Michigan, Colorado, New Mexico, Texas.

2011 electric revenue: $8.76 billion

Headquarters: Minneapolis

Ownership: Publicly traded

MIDAMERICAN ENERGY HOLDINGS CO.*

(U.S. regulated electric business units, MidAmerican Energy Co. and PacifiCorp)Electricity customers: 2.4 million

Territory: Iowa, Illinois, South Dakota (MidAmerican Energy Co.); Oregon, Washington, Utah, Wyoming, Idaho, California (PacifiCorp).

2011 electric revenue: $6.24 billion

Headquarters: Des Moines (MidAmerican Energy Co. and MidAmerican Energy Holdings Co.); Portland, Ore. (PacifiCorp)

Ownership: Part of the publicly traded holding company Berkshire Hathaway, headed by Warren Buffett.

* Regulated electric utilities only; company also has unregulated businesses.