The hydrogen fuel-cell cars being promoted as the future of zero-emission transport--aggressively by Toyota, slightly less so by Honda and Hyundai--generate quite a lot of controversy.
Now a new analysis by the Union of Concerned Scientists suggests that the wells-to-wheels carbon emissions of a fuel-cell vehicle running on hydrogen produced from natural gas is the same as that of a gasoline car returning 38 miles per gallon.
As an article in Technology Review notes, that's better than the 25-mpg average of new vehicles sold in the U.S. today--but not nearly as good as that of the 50-mpg Toyota Prius hybrid.
And the Prius is on sale today, for prices starting at about $21,000 for the smallest, least pricey member of the four-car Prius lineup, the Prius C subcompact.
2015 Toyota Prius C
In other words, suggests the article in its notably pithy title: "Forget hydrogen cars, and buy a hybrid" if you want to cut carbon cost-effectively.
There are, of course, many caveats to the suggestion.
One is that fuel-cell proponents note that hydrogen can be produced via a variety of pathways--including renewable energy.
The same can be said of electricity used to charge electric cars.
2016 Toyota Mirai hydrogen fuel-cell car, Newport Beach, CA, Nov 2014
It's also worth noting that the price of hydrogen vehicles will likely fall with volume production. The 2016 Toyota Mirai will be priced at $57,500 when it goes on sale in the second half of next year.
But it's also worthwhile noting that the same 38-mpg equivalent is the wells-to-wheel carbon footprint of a plug-in electric car charged on the worst, dirtiest, most coal-heavy grid in the U.S.
MORE: Electric-car wells-to-wheels carbon-emission equivalencies in MPG [Union of Concerned Scientists]
And of course the cleaner the grid, the lower the carbon emissions associated with operating that electric car.
That equivalency was calculated by an earlier report by the Union of Concerned Scientists, so the two figures should be comparable in methodology.
Let the debates continue.
[hat tip: Chuck Davis]