Hyundai has announced that its hydrogen Nexo and Tucson Fuel Cell SUVs have accumulated more than 8.4 million miles (13.5 million km) of driving across the United States.

There’s no doubt that the market for hydrogen-powered vehicles remains small, particularly due to the limited refueling infrastructure that makes them impractical to own. Nonetheless, the distance raked up by Nexo and Tucson models in the U.S. is the equivalent of 17 round-trip journeys to the surface of the Moon.

“Celebrating National Hydrogen Day 2019, we couldn’t be more proud of our NEXO and former Tucson Fuel Cell’s direct impact in reducing harmful greenhouse emissions in our planet,” vice president of Product, Corporate and Digital Planning, Hyundai Motor America, Michael O’Brien said. “As our hydrogen refueling infrastructure continues to grow in California and into the northeastern U.S., we eagerly anticipate the exponential reduction in emissions it will bring, resulting in a cleaner atmosphere for everyone.”

Also Read: Hyundai Delivers First Nexo In US, Undercuts Toyota Mirai By $65

Customer deliveries of the U.S.-market Hyundai Nexo kicked off in the final days of 2018 with a base price of $58,300, undercutting the Toyota Mirai by $65 before incentives from the state of California which are worth up to $5000. The hydrogen SUV is offered in Nexo Blue and Nexo Limited guises with the latter being more luxurious and costing a touch more. Range for the Nexo Blue sits at 380 miles (611 km) while the Nexo Limited can travel up to 354 miles (569 km) before owners have to find a hydrogen refueling station.

While many car manufacturers are focusing their attention on zero-emissions vehicles in the form of EVs, some, like Hyundai, Toyota, Honda, and Audi, are also working on hydrogen cars that are seen by many as the ultimate solution for zero-emission vehicles.