Whether you're a beginning investor or a near-retiree, the importance of purchasing stocks that pay dividends cannot be overstated. Not only do companies that have quarterly or annual payouts provide you with a steady stream of income, they also have the potential for capital appreciation. Simply put, dividend stocks can you give your portfolio what almost no other investment can -- both income and growth.

At The Motley Fool, we're avid fans of dividends -- and not just because we like that steady stream of cash. Studies have shown that from 1972 to 2006, stocks in the S&P 500 that don't pay dividends have earned an average annual return of 4.1%; dividend stocks, however, have averaged a whopping 10.1% per year. That is an incredible difference -- one that you'd be crazy to not take advantage of!

But investing in dividends can be dangerous -- companies can cut, slash, or suspend dividends at any time, often without notice. Fortunately, there are several warnings signs that may alert you, and these red flags could be the crucial factor in determining whether a company is likely to continue paying its dividend. Today, let's drill beneath the surface and check out NextEra Energy (NYSE: NEE).

What's on the surface?
NextEra Energy, which operates in the electric utilities industry, currently pays a dividend of 3.68%. That's certainly nothing to sneeze at, as the average dividend payer in the S&P 500, in 2009, sported a yield of 2%.

But what's more important than the dividend itself is NextEra Energy's ability to keep that cash rolling. The first thing to look at is the company's reported dividends versus its reported earnings. If you happen to see dividend payments that are growing faster than earnings per share, it may be an initial signal that something just isn't right. Check out the graph below for details of the past five years:

http://g.fool.com/img/editorial/NEEDividendPerShare.png


Source: Capital IQ, a division of Standard & Poor's.

Clearly, there doesn't seem to be a problem, here. NextEra Energy has been able to boost its earnings at an adequate pace and keep its dividends in check at the same time.

The more secure, the better
One of the most common metrics that investors use to judge the safety of a dividend is the payout ratio. This number tells you what percentage of net income is paid out to investors in the form of a dividend. Normally, anything above 50% is cause to look a bit further. According to the most recent data, NextEra Energy's payout ratio is 42.83%. It's obvious that, at least on the surface, there aren't any problems with NextEra Energy generating enough income to support that nice dividend of 3.68%.

More important than checking out the payout ratio may be simply taking a peek at NextEra Energy's cash flow. Free cash flow -- all the cash left over after subtracting out capital expenditures -- is used by firms to make acquisitions, develop new products, and of course, pay dividends! We can use a simple metric called the cash flow coverage ratio, which is cash flow per share divided by dividends per share. Normally, anything above 1.2 should make you feel comfortable; anything less, and you may have a problem on your hands. NextEra Energy's coverage ratio is -2.78, which isn't enough to make me feel comfortable as an investor. There could be a number of reasons the number is so low -- maybe it's typical for the industry, maybe there's a significant amount of debt coming due, or maybe NextEra Energy is simply less than stellar at managing its assets.

Either way, it's always beneficial to compare an investment with its most immediate competitors, so in the chart below, I've included the above metrics with those of NextEra Energy's closest competitors. In addition, I've included the five-year dividend growth rate, which is also a very important indicator. If NextEra Energy can illustrate that it's grown dividends over the past five years then there's a good chance that it will continue to put shareholders first in the future. Check out how NextEra Energy stacks up below:

Company

Dividend

Yield

Payout

Ratio

Coverage Ratio

5-Year Compounded Dividend Growth Rate

NextEra Energy

3.68%

42.83%

-2.78

6.95%

Exelon (NYSE: EXC)

5.24%

54.78%

1.44

6.89%

Dominion Resources (NYSE: D)

4.12%

42.34%

-0.39

6.20%

Duke Energy (NYSE: DUK)

5.69%

185.99%

-0.12

-2.69%

Source: Capital IQ, a division of Standard & Poor's.

The Foolish bottom line
Only you can decide what numbers you're comfortable with in the end; sometimes a higher yield and a higher reward means additional risk. However, when we look at NextEra Energy's payout ratio compared to its peer average, we see that it is a lower percentage, which illustrates that its dividend is probably more sustainable. The bottom line, however, is to make sure that with anything -- whether it be a dividend, a share repurchase, or an ordinary earnings report -- you do your own due diligence. Looking at all of the numbers in the best context possible is just the best place to start.