By Roger Conrad, Personal Finance

Utilities' formula for long-term growth is to invest in vital infrastructure and operate those assets in an efficient manner that generates a solid return on capital deployed. This simple strategy helped keep sector dividends rising during the credit crunch and recession of 2007-09.

Utilities expect to spend at least $2.4 trillion on power, gas, communications and water systems between now and 2030. That's a lot of fuel for further dividend boosts, which should push stock prices higher.

Companies strive to earn a reasonable return on capital expenditures. Those that meet this challenge will prosper and build shareholder wealth. Those that can't will become graveyards of capital for the unwary.

Sorting winners from losers is even more complicated today because large pieces of power, gas and even water industries are no longer operated as integrated monopolies as they were in decades past. Today, that means scrutinizing the unregulated side.

Exelon (EXC)
The key weakness at Exelon is that wholesale prices are tied to falling natural gas prices, a trend that has weighed on the company's results and stock price.

Fortunately, Exelon's successful acquisition of Constellation Energy Group for $7.7 billion earlier this year reduced the impact of a feared "earnings cliff," as Exelon's selling price hedges come off.

That's why we expect the stock's projected earnings per share of $2.55 to $2.85 for 2012 to represent a bottom for the year, even though they'll still comfortably cover the 5.5% dividend. Exelon Corp. -- a new addition to our Income Portfolio -- is a buy up to $45.

Atlantic Power (AT)
Atlantic Power derives all of its income from selling power into wholesale markets throughout North America.

Fortunately, almost all capacity is locked up under long-term contracts. And thanks to last year's merger with the former Capital Power LP, the company has diversified its revenue streams.

Atlantic's second-quarter cash flow rose 70% from the same quarter last year. The company also expects a fourth-quarter opening of a major wind plant in Oklahoma anchored by a 20-year contract with OGE Energy Corp.

Atlantic pays dividends from cash flows rather than earnings per share. That enables it to dish out more aggressively, with a 90% to 97% payout ratio expected for full-year 2012 and a yield in excess of 8%.

Atlantic also owns the regulated Path 15 power line in California, while Exelon runs power distribution operations in Illinois, Maryland and Pennsylvania. Both companies' dividends held in 2008-09, with Atlantic raising its payout in late 2011. Atlantic Power's American depositary receipt is a buy below $16.

NRG Energy (NRG)
NRG Energy is a third unregulated power stock to consider. The company is attempting to acquire battered rival Genon Energyin a deal that will make it by far America's biggest producer of wholesale electricity. That deal is expected to close in the first quarter of 2013.

In the meantime, NRG has initiated a quarterly dividend of $0.09 per share for the first time in its history. After doubling its cash flow from year-ago levels, NRG Energy covered this inaugural payout by an ample margin.

As with all wholesale power producers, NRG's stock has suffered the past five years, losing more than half its value. But with well-run assets and a solid balance sheet, it's poised for a reversal of fortunes. Buy NRG Energy up to $22.

Unregulated earnings mean these stocks are riskier than the more regulated utilities, but this risk is well reflected in their stock prices, making Exelon, Atlantic and NRG excellent fresh horses for another utility stock run.

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