Investing isn't easy. Even Warren Buffett counsels that most investors should invest in a low-cost index like the S&P 500. That way, "you'll be buying into a wonderful industry, which in effect is all of American industry," he says.

But there are, of course, companies whose long-term fortunes differ substantially from the index. In this series, we look at how individual stocks have performed against the broad S&P 500.

Step on up, Wisconsin Energy (WEC 0.78%).

Wisconsin Energy shares have outperformed the S&P 500 over the past quarter-century, and with less volatility:

Source: S&P Capital IQ.

Since 1987, shares have returned an average of 10.9% a year, compared with 9.7% a year for the S&P (both include dividends). One thousand dollars invested in the S&P in 1987 would be worth $19,200 today. In Wisconsin Energy, it'd be worth $27,600.

Dividends accounted for a lot of those gains. Compounded since 1987, dividends have made up about 70% of Wisconsin Energy's total returns. For the S&P, dividends account for 39% of total returns.

Now have a look at how Wisconsin Energy earnings compare with S&P 500 earnings:

Source: S&P Capital IQ.

Some underperformance here, but that's expected from a utility. Since 1995, Wisconsin Energy's earnings per share have increased by an average of 4.3% a year, compared with 6% a year for the broader index.

What's that meant for valuations? Wisconsin Energy has traded for an average of 16 times earnings since 1987 -- below the 24 times earnings for the broader S&P 500.

Through it all, shares have been strong performers over the past quarter-century.

Of course, the important question is whether that will continue. That's where you come in. Our CAPS community currently ranks Wisconsin Energy with a three-star rating (out of five). Care to disagree? Leave your thoughts in the comment section below, or add Wisconsin Energy to My Watchlist.