An inexpensive stock price doesn't tell us any more about a company than a high stock price. After all, a company's market cap is simply the share price times shares outstanding no matter what the price of a stock is. 

But in reality, companies try to stay away from having stock prices that are too low. Penny stock territory is a warning sign for investors, and even prices under $20 can be seen as a sign of weakness by investors. But I think there are still buys in the low share-price segment of the market, and Virgin Galactic (NYSE:SPCE), Bloom Energy (NYSE:BE), and SunPower (NASDAQ:SPWR) are the three I am very bullish on long term. 

Virgin Galactic's Mach 3 aircraft concept drawing.

Image source: Virgin Galactic.

Redefining travel

There hasn't been a lot of change in air travel over the last half-century, but that may be about to change now that space, or sub-space, travel is here, and Virgin Galactic is leading the way. The company is starting by offering space tourism flights to buyers able to spend $250,000 on a ticket, but that's just the start of the company's growth plans. 

Virgin Galactic is developing an aircraft that could travel at Mach 3 at 60,000 feet, enabling a flight from Los Angeles to Tokyo in three or four hours instead of today's 12-hour flight time. Supersonic travel has been tried by the Concorde aircraft from New York to London, and that ultimately failed. There are also restrictions in supersonic travel over land in some locations, but I don't think that will hold the company back. With a capacity of between nine and 19 people, think of Virgin Galactic's supersonic travel more like a long-range, high-speed private jet than a competitor to a jumbo jet. If you look at it that way, the potential six-figure price tag makes more sense. 

For the time being, Virgin Galactic isn't generating revenue in its pre-commercial form and is still a high-risk stock. But with a stock price below $20 and a potentially multi-billion dollar market in front of it, this is a high-growth stock I'm holding onto long term. 

An energy disruption in the making

Like travel, there haven't been a lot of changes in the energy industry in the past century. But the maturation of wind and solar energy as cost-competitive energy sources versus fossil fuel has driven the need for new technologies like long-duration energy storage and ways to use renewable electricity as fuel. That's where Bloom Energy's fuel cells and new electrolyzers could open up a massive new market in energy. 

What could make Bloom Energy a truly disruptive company is its ability to produce hydrogen cost-effectively with an industrial electrolyzer. This would take (likely renewable) electricity and water as inputs and output hydrogen that could be used at a later time as fuel. 

Bloom Energy already makes fuel cells that could turn that hydrogen into electricity at commercial buildings or utilities, but it's also working on using fuel cells in new applications like large ships. This could change how we produce and consume energy forever. 

Home with a large solar installation on the roof.

Image source: Getty Images.

Finding its way in solar energy

SunPower has spent most of the last decade trying to decide what it wants to be in the solar industry. The company started by manufacturing high-efficiency solar panels, then moved into utility-scale project development, developed an inverter, and built a large residential and commercial solar business. After the spinoff of its manufacturing business later this week into Maxeon Solar Technologies, SunPower will finally be focused on one core business: residential and commercial solar solutions. 

The company isn't going to be the installer of solar on rooftops but rather provide solutions to third-party installers who will do the installation. In residential solar, the company provides installation plans and quotes in under a minute online and can refer those leads to local partners. It does more development in the commercial space but is still more of a technology provider than an installer. 

What this strategy allows SunPower to do is build technology that can scale as its customers and end-market scales. And it should lead to lower costs than vertically integrated solar installers. But what I'm most excited about is the addition of energy storage in residential and commercial offerings, which could make SunPower a big player in competitive power markets and be a long-term revenue generator from solar and storage installations. 

SunPower still isn't profitable and has a lot of work to do in realizing its potential, but after years of searching for its place in the solar industry, I think it has a winning strategy on its hands. 

Cheap stocks can be big winners

You'll notice here that all of these companies are high-potential and high-risk companies. And that's often the case with stocks trading under $20. But given their growing markets and leadership positions, I think Virgin Galactic, Bloom Energy, and SunPower are all built to be great stocks long term. 

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.