Let's face it, dividends aren't all that sexy. While rule-breaking stocks may zoom up or down 100% in a year's time, dividends are the tortoise to the rule-breaking hares.

But if anyone had a doubt about the power of dividends, they need only read Jeremy Siegel's The Future for Investors. In it, he writes: "Dividends matter a lot. Reinvesting dividends is the critical factor giving the edge to most winning stocks in the long run."

An important metric for dividends
The utility sector, in particular, is a gold mine for dividend investors, where the average industry yield is about 4%. Knowing how important dividends can be, it's important to examine how sustainable a company's dividend is.  

One of the most popular metrics used to measure a dividend's sustainability is the earnings payout ratio. In essence, this measures how much of a company's earnings are used up in paying out dividends. As theory goes, the lower the payout ratio is, the more sustainable the dividend is.

Take a look at the table below. It includes seven popular utility stocks and their payout ratios.

Company

Dividend Yield

Earnings Payout Ratio

OGE Energy (NYSE: OGE) 2.9% 24%
CMS Energy (NYSE: CMS) 4.2% 49%
Great Plains Energy (NYSE: GXP) 4.0% 59%
PPL (NYSE: PPL) 5.0% 60%
Aqua America (NYSE: WTR) 2.7% 62%
CenterPoint (NYSE: CNP) 4.1% 69%
Southern Co. (NYSE: SO) 4.7% 81%

Source: Yahoo! Finance.

In their book Million Dollar Portfolio, David and Tom Gardner suggest that you should only hold stocks that have a payout ratio of less than 65%. Clearly, this would make the cautious Fool worry about the sustainability of dividends from companies such as CenterPoint and Southern (this hasn't, however, stopped Southern from being an active recommendation in the Motley Fool's Income Investor newsletter).

But wait, there's more!
This is where things get tricky. Because earnings are reported using the accrual method, all of the money that a company says it's earned hasn't necessarily been paid to it yet. Things like accounts receivable and payable, depreciation and goodwill are included in earnings -- and they don't immediately affect the amount of money a company has in the bank.

The good news is that there is -- in fact -- a way to check how much money a company has put in the bank: free cash flow. This number is very (some Fools say more) important in evaluating a company's dividend sustainability. In the end, dividends are paid from free cash flow, not from earnings.

Check out the free cash flow payout ratio for these companies, and the story changes considerably.

Company

Free Cash Flow Payout Ratio

OGE Energy Cash flow negative
CMS Energy 55%
Great Plains Energy 204%
PPL Cash flow negative
Aqua America Cash flow negative
CenterPoint Cash flow negative
Southern 1,190%

Source: Yahoo! Finance.

Wow! That really changes things. Using earnings to calculate payout ratio, we had five safe dividends earlier in the article, but when we dove into free cash flow -- which is what dividends are paid from -- we see that we only have one safe play left: CMS Energy.

How can this be?
It's no secret that capital expenditures are enormous for utilities, and when a company needs to build out or improve upon their existing infrastructure, cash flow can disappear.

Sometimes this is just a short-term problem, but other times, it's a serious cause for concern. Let's take a look at these companies' average annual free cash flow over the past five years.

Company

Average Annual Free Cash Flow

OGE Energy ($216 M)
CMS Energy $169M
Great Plains Energy ($311M)
PPL $236M
Aqua America ($56M)
CenterPoint $40M
Southern $417M

Again, things change a ton when we look at dividends from a third point of view. Take Southern, for example. The company has sky-high payout ratios over the past year when looking at earnings and cash flow. But when we zoom out and look at five-year averages, we see that Southern produces the most free cash flow by far of the group.

Foolish takeaway
If you're looking for some dividend ideas, consider 13 names from a free report from Motley Fool's expert analysts called "13 High-Yielding Stocks to Buy Today," including one named by a senior retail analyst as "the dividend play of a lifetime." Tens of thousands have requested access to this report, and today I invite you to download it at no cost to you. To get instant access to the names of these 13 high-yielders, simply click here -- it's free.

Fool contributor Brian Stoffel doesn't own any shares discussed in the story. Motley Fool newsletter services have recommended Aqua America and Southern.

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