How does hydrogen compare?

Just a few years ago, hydrogen was all the rage as a leading contender among petroleum alternatives. Researchers were rapidly making progress on low-temperature fuel cells — electrochemical devices that react hydrogen and air into electricity and water vapor. Visionaries such as Geoffrey Ballard put their laboratory breakthroughs on the road in fuel cell buses, garnering attention from governments and venture capitalists willing to buy into hydrogen’s promise of Powering the Future.

It turned out that hydrogen fuel cell vehicles (FCVs) weren’t quite as ready for prime time as many — including former President George W. Bush — thought. Fuel cell research had ramped up under the Clinton Administration, when it was funded as one among several long-term options in the billion-dollar supercar program. At the time, the Detroit automakers and their administration partners were mainly touting the tripled-efficiency diesel hybrids they promised to have road-ready by 2003.

The “forever fuel” rose to the fore when the Bush team took charge. The administration made hydrogen FCVs a centerpiece of its green initiatives, blessing the program with nearly another billion taxpayer dollars and giving it the flag-draped name FreedomCAR. During a State-of-the-Union address, President Bush left us with the memorable quote that “the first car driven by a child born today could be powered by hydrogen and pollution-free.”

Well, that was in 2003. Today most of those 7- and 8-year olds are probably hearing a lot more about battery electric cars and plug-in hybrids. But a few of them may be in the handful of lucky Southern California families now running errands in the Honda FCX Clarity, the first hydrogen FCV certified for public leasing in the United States.

With no CO2 or other pollution coming from its tailpipe, the FCX Clarity is a zero-emission vehicle (ZEV) and achieves 60 miles (both city and highway) per kilogram of hydrogen. The car carries its hydrogen fuel as a gas compressed to 5,000 pounds per square inch (psi), or about 340 times normal air pressure. A kilogram of hydrogen contains just about as much energy as a gallon of gasoline, so the Clarity is effectively a 60 mpg vehicle; with a tank capacity of 4.1 kilograms, it can travel 240 miles per fill up.

Honda FCX Clarity at a demonstration hydrogen filling station in California

Like electricity, hydrogen is now derived from fossil fuel, mainly natural gas. As for other ZEVs, its true environmental story can’t be told without tallying the upstream pollution that occurs when making the hydrogen. On a current national average basis (the way that AutoEcoRating works), producing hydrogen pollutes less than generating electricity but still more than refining gasoline, per unit of energy delivered to a car.

Thus, the FCX Clarity gets an eRating of 194, well ahead of most other midsize cars, but not quite enough to beat the Toyota Prius eRating of 205.

Relative to the average midsize car and its eRating of 106, the Honda FCX Clarity has 45 percent less environmental impact, and that’s with today’s fossil-based hydrogen compared to fossil-based gasoline.

As a fully functional sedan, the Honda FCX Clarity’s 194 eRating nearly matches the 195 eRating of the smaller, more range-limited Nissan Leaf. This illustrates why proponents (including many car company researchers) still see great promise in FCVs, which don’t face the struggle that EVs face as battery limitations become more burdensome when vehicles go up in size.


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