Before you think "boring utility," please look at this return: 61%. That's how much diversified energy company Constellation Energy (NYSE:CEG) has risen since it was recommended in our July 2004 issue of Motley Fool Income Investor.

And if you find strong results tedious, don't read the second-quarter report that Constellation released this morning. Compared to the year-ago quarter, revenue increased 26.8%. Earnings, excluding special items, soared 22%.

Income per share beat the high end of company guidance (which just happened to match the mean analyst estimate) by $0.04 a share, coming in at $0.66 after special charges.

The company's Baltimore Gas & Electric business chipped in $0.13 a share, unchanged from last year's comparable quarter. The merchant energy business, a nasty sector that has sent others to bankruptcy court, turned in another strong performance, contributing $0.51 vs. $0.42 a share (after special charges) in the year-ago quarter. Constellation, among other things, is the U.S.'s largest seller of wholesale power. The last two cents were contributed by non-regulated businesses.

The company reaffirmed its 2005 earnings guidance of $3.35 to $3.60 per share, up from $3.24 (excluding special items) earned last year. The mean analyst projection is $3.49 a share, valuing the stock at 17.4 times forward earnings.

Don't jump to the conclusion that Constellation's future holds strong double-digit earnings growth. Over the next five years, analysts expect the company to compound earnings at 9% a year (which, to be fair, is better than the 6.6% the company managed over the last 5 years). This year's second-quarter percentage gain seems especially high because Q2 earnings last year fell to $0.54 a share after special charges.

Relatively speaking, how does Constellation's long-term performance compare to its peers? Look at a one-decade chart of Constellation, and you see the 2001-2002 doldrums when "merchant power" was a dirty word. But today, Constellation is selling at a new all-time high. Contrast that with Duke Energy (NYSE:DUK), which would need a 50% gain just to get back to 2001's high. The charts are equally ugly for Allegheny Energy (NYSE:AYE) and American Electric Power (NYSE:AEP).

The point of discussing competitors is not to note that Constellation is winning an ugly baby contest. On the contrary, Constellation has built a strong presence in merchant power, and Wall Street has rewarded shareholders with a 59.1% rise in the company's stock price over the last 52 weeks.

Though Income Investor plucked this merchant-power star from obscurity, its great value proposition has faded. The stock's rise has also lowered the dividend yield to a less-than-tempting 2.05%. Those seeking big percentage gains in the future would be wise to look elsewhere.

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Fool contributor W.D. Crotty does not own shares in any of the companies mentioned. Click here to see the Motley Fool's disclosure policy.