Is Tesla Stock a Buy in September 2026?

Tesla (NASDAQ: TSLA) just took a major step toward the future investors have been waiting for.

The Cybercab, Tesla's self-driving taxi, is no longer a concept on a stage. Tesla has begun offering paying customers in Austin, Texas, the opportunity to ride in its steering-wheel-free, pedal-free autonomous vehicles.

That makes this an interesting moment for Tesla investors, as the future it has been promising for years seems increasingly tangible.

But does that make the stock a buy in September?

Image source: Getty Images.

Tesla is finally moving from promise to product

For years, Tesla's biggest opportunities existed mostly in the future. Robotaxis were coming. The humanoid robot Optimus was coming. Artificial intelligence would eventually transform the company.

Now some of those projects are beginning to arrive in tangible ways. In its second-quarter earnings release, Tesla said it had expanded its Robotaxi service to seven U.S. markets, and noted that production of the Cybercab has begun. The company also expects to begin production of Optimus soon.

Those aren't just promises anymore. They're early-stage commercial products and businesses.

If autonomous transportation becomes a massive market and Tesla captures a meaningful share of it, the electric vehicle (EV) business that accounts for most of the company today could eventually serve as the foundation for something much larger. The same is true for Optimus. Humanoid robots capable of performing useful work at scale could open a market that is difficult to quantify today. The potential is enormous.

But potential isn't the same as earnings.

The Cybercab is an important test

The most important question for Tesla investors isn't whether the Cybercab can drive itself. It's whether Tesla can turn autonomous driving into a high-return business. That's a much higher bar.

Currently, the rollout of those vehicles remains limited. And almost immediately after Tesla began putting passengers into Cybercabs, the National Highway Traffic Safety Administration opened an audit to examine Tesla's self-certification and investigate whether the unusual vehicle complies with federal safety standards.

That doesn't mean the Cybercab will fail. But it does mean that its commercialization isn't simply a matter of manufacturing more EVs. Tesla will need to successfully navigate regulatory, safety, insurance, customer adoption, fleet operations, and economic considerations.

Even the company acknowledged that scaling its Robotaxi arm quickly is not the main priority -- scaling safely is. That's precisely why the next phase of the process could go more slowly than investors want.

Tesla is spending heavily on the future

There's another reason I wouldn't chase the stock. Tesla is spending aggressively now, well ahead of its biggest new businesses reaching meaningful scale.

The company expects its 2026 capital expenditures to exceed $25 billion, and says that spending will continue to grow over the next two to three years as it expands its Robotaxi fleet, Optimus production, semiconductor capacity, AI compute, solar power system manufacturing, and other infrastructure.

The impact of these investments is already being reflected in its financials. In the second quarter, the company's free cash flow was negative $1.1 billion.

The silver lining is that the cash and investments on its balance sheet totaled roughly $44 billion, and it has almost no debt. So, this free cash outflow isn't creating a balance sheet emergency.

In other words, Tesla can afford to spend heavily, but we have very little clarity about whether these investments will generate long-term shareholder returns.

That's where valuation becomes important

With a market capitalization of roughly $1.1 trillion (as of this writing) and trading at a price-to-sales (P/S) ratio of 12.1, Tesla isn't priced like an ordinary automaker. That valuation assumes Tesla will become much larger.

For perspective, peer automaker General Motors has a P/S ratio of 0.5.

Investors are effectively assigning substantial value to autonomous transportation, robotics, AI, energy, and software businesses that aren't yet producing anything close to the revenues and profits that it will take to justify this valuation.

That's what makes investing in Tesla's stock difficult. If Tesla management is right about the potential of Robotaxis and Optimus, the current stock price could eventually look cheap in retrospect. If they are even modestly wrong about the timing or the potential market opportunities, however, the stock could struggle.

And that's an important point. Tesla doesn't need to fail for the stock to disappoint. The stock could suffer if the company merely succeeds more slowly than investors expect.

Should you buy Tesla stock in September?

For me, Tesla is a stock to watch rather than chase.

The company has made genuine progress. A few Cybercabs are now carrying paying passengers. The company's Robotaxi operations are expanding, and Optimus is moving toward production. Those developments make Tesla's long-term story more credible than it was a few years ago.

But they haven't yet proved that Tesla can generate the enormous profits required to justify its current valuation. That's the distinction investors need to keep in mind.

In short, investors who buy the stock today are paying a premium for a future that is becoming more real, but one that hasn't fully arrived.

Lawrence Nga has no position in any of the stocks mentioned. The Motley Fool has positions in and recommends Tesla. The Motley Fool recommends General Motors. The Motley Fool has a disclosure policy.