There's an old joke about hydrogen power: It's the fuel of the future, and always will be. Elon Musk doesn't just agree, he called out hydrogen fuel cell vehicles as "bullshit," claiming they're more of a marketing ploy for automakers than a long-term solution.

The comment from Musk came during a speech to employees and enthusiasts at a new Tesla service center in Germany. The electric automaker's co-founder and CEO was onstage espousing the virtues of the Model S when he went off on a tangent about EV naysayers: "And then they'll say certain technologies like fuel cell ... oh god ... fuel cell is so bullshit. Except in a rocket."

Musk goes on to state that even given the very best hydrogen technology, it doesn't come close to the energy density of a modern lithium-ion battery pack like that found in the Model S.

Granted, Musk is a bit biased and firmly entrenched in the battery electric vehicle space, but despite years of promises from automakers and government agencies, it's tough not to think that the zero emissions future promised by hydrogen is still a long way off.

That hasn't stopped a range of automakers – from Honda to Mercedes-Benz – from continuing to develop hydrogen-electric vehicles.

Honda has continued to champion the use of hydrogen with its FCX Clarity, a functioning concept car that's been out for a few years and was even leased to a select group of prominent Southern California residents in 2010.

In 2011, Mercedes ran around the world in modified B-Class subcompacts to espouse the virtues of hydrogen and solidify its commitment to the fuel. But in the interim, we haven't heard much from either automaker, and the infrastructure necessary has never materialized, despite it being the most abundant element on Earth.

In the video above, Musk's comments start at the 29-minute mark. Best to fast forward unless you speak German.