Batteries are expensive. Additionally, batteries add heft and mass, which lowers the mileage. The weight of the battery pack of some of the early Tesla Roadsters came to 1,000 pounds. While chemical and electrical engineers continue to improve them, progress comes slowly. J.B. Straubel, the CTO of Tesla Motors, has said that batteries roughly double in performance every ten years, or about five times slower than Moore’s Law.
Enter hydrogen. In a hydrogen fuel cell car, hydrogen gets drawn through a catalytic membrane: an electron gets stripped from the hydrogen to power the car. The waste product—water—goes out the tailpipe. The crucial component is a thin membrane laced with expensive elements that helps conduct the chemical reaction. The fuel cell stack, in theory, can weigh less than batteries. Filling fuel cell cars—assuming a refueling station is nearby—takes minutes, not the hours needed for a typical EV.