Can you become a millionaire by investing in Energy Transfer (ET 0.84%) stock? Absolutely. Over the long term, shares have proven a terrific investment. And given the company's unique asset base, there's a good chance this performance will be repeated in the years to come.

There's only one catch: If you don't invest in this stock in a certain way, you may forfeit your chance of reaching the $1 million mark.

1 way Energy Transfer stock can make you a millionaire

Since 2006, Energy Transfer's stock price has risen by just 187%. The S&P 500, meanwhile, produced a total return of 489%. On the surface, Energy Transfer hasn't proven a great long-term investment. But this is why it's critical to look at a stock's total return, not just its share price movement. Total returns account for actions that can affect shareholder profits -- like dividends and spinoffs -- but that aren't necessarily reflected accurately in the stock price.

For its part, Energy Transfer has been a prolific dividend payer. The current dividend yield is around 8%. These big dividends aren't included in the stock price movement. In fact, they tend to depress the stock price, given the reduction of cash on the balance sheet.

When including dividends in Energy Transfer's total returns, shares produced an 882% profit for shareholders since 2006. That's nearly double the S&P 500's total return over that time period. This type of return can help everyday investors become millionaires. It would still take several decades of consistent saving, but by investing in stocks like this, you can produce returns that transform a few thousand dollars a year into a sizable retirement nest egg. Just don't forget to retain and reinvest your dividends.

The only remaining question is: Will Energy Transfer stock remain a long-term winner?

ET Chart
ET data by YCharts.

Can you still rely on Energy Transfer stock?

Energy Transfer stock has proven its ability to generate long-term returns that can make you a millionaire. But is Energy Transfer stock still a good option today? Absolutely. That's because this company has a durable, structural advantage when it comes to generating profits.

At its core, Energy Transfer is considered a midstream energy business. That means it's involved not in the production of fossil fuels, but in their transport, refining, and storage. Around 90% of the company's earnings are fee-based, meaning it earns money based on the volume of services provided, not the underlying price of the fossil fuel in question. Its facilities are expensive to build and difficult to replicate. And because it provides necessary services to oil and gas producers in a way that insulates the company from commodity price swings, Energy Transfer can pay a reliable dividend to shareholders.

Note that Energy Transfer isn't completely insulated from commodity markets. In 2020, it was forced to slash its dividend due to pandemic uncertainty. This cut proved conservative, however, and roughly a year later, the payout returned to its previous level.

"Overall," concludes Fool writer Geoffrey Seiler, "Energy Transfer is well positioned to be a steady performer throughout different commodity cycles, given that it is involved in predominantly fee-based activities that are diversified across product types." And because the company's infrastructure spans more than 20 U.S. states, Energy Transfer also has the unique ability to capitalize on price discrepancies across local and regional markets.

Because Energy Transfer is completely dependent on long-term fossil fuel demand, it is important to include this stock in a broad basket of investments diversified across other sectors and end markets. But if you're looking to build a portfolio capable of producing significant recurring income over the long term, Energy Transfer stock remains a great pick.

Just remember that this will require a long-term investing plan of your own. These types of stocks require consistent saving over long periods of time to produce the magic of compound interest.