Edison International is the parent company of 3 subsidiaries: Southern California Edison, Southern CA's largest electric utility, which benefits from friendly state regulation; Edison Mission Energy, a group of low-cost merchant generating plants in the midwest (generating more than half the company's profits); and Edison Capital, which invests in renewable energy and other tax-efficient investments.

Entergy is an integrated energy company with 3 primary businesses: a regulated utility that distributes power and gas across a 4-state area; a non-utility nuclear division that sells power in the northeast merchant market, with big cost advantages over gas-fired plants; and an energy commodity services division that generates and sells non-nuclear wholesale power. The company mitigates merchant generation risk by selling its output in long-term power purchase agreements. ETR plans to spin off that business into a separate publicly-traded corporation known as Enexus Energy, which will operate 5 merchant generator nuclear power plants.

NRG Energy is a wholesale power-generation company that operates a broad portfolio of power plants in 5 countries. It's also involved in energy marketing, and trading and fuel procurement. Most of its assets are in the U.S. (mainly the northeast, TX & CA), and its recent acquisition of Texas Genco gives it a scale advantage over its peers. NRG emerged from Chapter 11 bankruptcy as a stand-alone company in 2003.

Public Service Energy Group is the holding company for a regulated utility that delivers energy service in New Jersey; a competitive energy supplier that owns and operates low-cost and "low-carbon profile" nuclear, coal and natural gas powered plants, selling wholesale electricity in the high-priced Mid-Atlantic and Northeast markets; and an energy investment firm that owns and operates energy-related assets globally. The merchant business generates 2/3 of profits, and should continue driving earnings as long as efficiency levels and power prices remain at or above current levels.

Huaneng Power International develops, constructs, operates and manages plants in China, and is that country's largest electricity producer. It owns 16 plants, has controlling interests in 13 companies, and has minority interests in 5 more. Although riskier than the others, it appears to be poised for profitability going forward.