Can We Really Build Cars That Run Only On Water?

While it is certainly enticing when a company or individual claims that they have developed technology that can power cars purely on the water when it comes to science, there is a fundamental restriction to this very idea. Simply put, energy can neither be created nor destroyed (it can only be transformed from one form to another). Water cannot burn, so the only way to derive usable energy is by splitting water into hydrogen and oxygen.

As covered in the video, the problem in doing so is that the amount of energy spent separating water into constituent elements is more than the energy you get back when they recombine inside the fuel cell. Basically, you have to spend more energy converting water to fuel than you will receive as fuel.