Investors who have been able to take the emotion out of investing, find and own great businesses, and stick to a long-term time horizon have had little trouble earning healthy annualized rates of return on their investments. Simply put, the data show that buy-and-hold investing is one of the simplest and best strategies to build wealth. And that means it'll probably continue to be one of the best strategies.

With that in mind, we recently asked three contributors at The Motley Fool for one of their best stocks to buy and hold for the next two decades. Here's why they chose Enphase Energy (NASDAQ:ENPH), Welltower (NYSE:WELL), and Microsoft (NASDAQ:MSFT).

Rooftop solar panels.

Image source: Getty Images.

Finally profitable and rapidly growing

Maxx Chatsko (Enphase Energy): Considering this solar stock is trading at a historically expensive valuation relative to book value right now, a long-term mindset might be the only way to rationalize new purchases of shares. But that's not such a bad thing.

The amount of electricity that utility-scale and small-scale solar installations provide in the United States grew 25% year over year in 2018, according to data published by the U.S. Energy Information Administration. That means solar power generated about 2.5% of the country's electricity last year. The EIA expects that figure to grow another 35% by the end of 2020, although most past estimates have actually underestimated solar's growth. 

The point is that an annual growth clip in the double digits is expected to continue for solar energy for the foreseeable future -- and that's great news for Enphase Energy. The company engineers and supplies various hardware components that make solar modules work seamlessly with existing grid infrastructure or a new energy storage device. The business finally became profitable in the fourth quarter of 2018 and expects significant growth in the year ahead. In fact, it's growing so quickly that some of its parts suppliers are having trouble keeping up.

Enphase Energy expects first-quarter 2019 revenue to soar 32% from the year-ago period, thanks in part to the ramp-up of a supply contract that will see its microinverters put into solar modules that SunPower manufactures. That deal alone will add about $65 million in annual revenue at a gross margin of 34% once the supply spigot is fully opened at the end of this year. When combined with growing demand from all other customers, it's no surprise the business expects to be comfortably profitable.

That said, fourth-quarter 2018 operating margin was still just half of management's long-term goal, which suggests there's plenty of profit growth ahead for shareholders. Executing on that goal will allow the business to improve its financial flexibility through efforts such as paying down debt, financing growth initiatives from operations, and lowering its earnings-based leverage metrics. That could make Enphase Energy's current $900 million valuation quite the bargain 20 years from now.

An arrow rising up shelves on a wall.

Image source: Getty Images.

Betting on a hot future trend

Neha Chamaria (Welltower): In an October 2018 report, the U.S. Census Bureau estimated that the global population of people 65 and older will hit 1 billion by 2030 and 1.6 billion by 2050, up from from 617.1 million in 2015. In another report, the Census Bureau predicts that the elder population will "outnumber children for the first time in U.S. history" within the next 20 years, as baby boomers age.

One industry that could leap forward as the population ages is healthcare. As the largest publicly listed healthcare real estate investment trust (REIT) in the U.S., Welltower should be a key beneficiary.

Welltower owns more than 1,600 healthcare properties that offer seniors housing, outpatient medical, and post-acute-care services. The company's portfolio has undergone a sea change in recent years as management prioritized growth in senior housing, particularly in upscale urban markets including Los Angeles, New York, Boston, and London, among others. In fiscal 2018, Welltower spent nearly $3.4 billion on acquisitions.

So while end market dynamics should offer big opportunities for Welltower to grow -- and any growth should eventually be reflected in the stock price -- investors can also earn solid dividends. As a REIT, Welltower is required to pass on at least 90% of its taxable income to shareholders in the form of dividends. If not for those dividends, Welltower stock's returns wouldn't have been as high in recent years. Overall, this 4.6% yielding stock makes for a perfect candidate to buy and hold for at least 20 years.

A man drawing a flowchart.

Image source: Getty Images.

Not your father's Microsoft

Chris Neiger (Microsoft): It may be tempting to think Microsoft's best days are behind it. In truth, the company has made a solid transition from its old software-peddling days to a cloud computing juggernaut.

Recent data shows that the company has 16.5% of the public cloud computing market, putting it behind the current leader, Amazon.com, and well ahead of Alphabet's Google. That makes Microsoft a stock to buy and hold for decades because cloud computing is one of the most important tech trends right now and will grow into a $278.1 billion market by 2021.

And Microsoft isn't just gaining market share from its cloud pursuits. It's generating massive sales from its cloud segments as well. At the end of the company's most recent quarter, Microsoft's commercial cloud sales reached $9 billion, up 48% from the year-ago quarter, and its public cloud business, Azure, saw its sales spike 76%.

What makes Microsoft even more appealing is that the company grew overall sales by 12% in the most recent quarter, and earnings per share were $1.08, up from a loss of $0.82 in the year-ago quarter. Think about that for a second: A company that was once synonymous with Windows software for decades has successfully transitioned to become one of today's most significant tech opportunities -- and it's still putting up impressive growth figures to boot.

If you're still on the fence about Microsoft's stock, then consider that the tech giant also pays a solid 1.6% yield to its shareholders. And with the company already delivering 15 consecutive years of dividend increases, Microsoft investors will surely benefit from the company's shareholder payouts -- and its overall growth -- for years to come.