Image source: Tesla Motors.

Pick an electric car -- any electric car. Chances are, you just envisioned a Tesla Motors (NASDAQ:TSLA) Model S. Understandably, since more Model S units have been sold this year than any other electric-car model. But Tesla Motors isn't speeding ahead alone in the unconventional car category, and its biggest competitor just got serious. Here's what you need to know.

The greenest goal yet
Tesla Motors has bet the bank on building out the electric vehicle market. So far this year, it's sold 17,300 Model S vehicles, 30% more EVs than its closest competition. Tesla has also built out its own exclusive electric vehicle infrastructure and is roaring ahead on improving its battery systems and cutting costs with its new Gigafactory.

Tesla has done such a good job convincing everyone of the electric car revolution that it can seem like hybrids are for gasoline hedgers, and other alternative vehicles are concept cars that will never hit the market. But that's not necessarily true.

Two weeks ago, Toyota Motor Corporation (NYSE:TM) announced a series of aggressive new goals: zero CO2 emissions at all plants by 2050, improved factory wastewater management, the establishment of recycling centers for old cars in Japan, conservation projects, and zero life-cycle emissions for its vehicles. But there's one additional goal that could put Toyota Motor Corporation bumper to bumper with Tesla: The Japanese automaker has vowed to reduce its new-car CO2 emissions by a whopping 90% (compared to 2010 levels) by 2050. How so? By essentially eliminating its gasoline-powered fleet. 

Non-gas guzzlers
Famous for bringing hybrid vehicles to the mass market, Toyota Motor Corporation is ready to scale again. And just as it did with hybrids, it's ready to be the first mover on an entirely different technology: fuel cells. We don't hear much about fuel cell-powered vehicles in the U.S., and for good reason: For all intents and purposes, there aren't any. Historically, production costs have proven too high for fuel-cell cars to be competitive. But Toyota, with a robust R&D team and some of the most efficient production lines in the world, has changed all that with the Mirai. After launching in Japan late December, these vehicles that guzzle hydrogen and emit purified water from their tailpipes just hit the American and European roads this month.

Image source: Toyota Motor Corporation.

While the Mirai is just now hitting markets (orders are up to 1,500 in Japan), Toyota expects to sell more than 30,000 annually by 2020. That's peanuts compared to its 1.5 million estimated annual sales for its hybrid vehicles, but the Mirai will enjoy near-zero competition as it expands the fuel-cell market. 

Toyota vs. Tesla
Toyota's Mirai launch means the fuel-cell car has officially made the move from concept car to market-ready. Tesla Motors should be worried. Tesla has banked its reputation on being the best at what it does. Its technology is patent-free, presenting the challenge to any automaker to out-innovate its engineers. But Toyota is ramping up an entirely new technology, and if it turns out that fuel cells are simply better than electricity-storing batteries, Tesla will be left with nothing to charge.

An investor's advice
As a Tesla Motors shareholder myself, I'm not selling today. Or tomorrow. But Toyota's latest announcement deserves special attention, and I'll be keeping my eye on fuel-cell technology and vehicle sales in the years to come. Tesla Motors' competition just got a whole lot more serious, and Toyota Motors deserves a close watch.

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.