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Over the past two weeks, multiple people have sent me a story about a supposed water-powered car and asked for comment. The story varies, but one widely shared version on Facebook claimed:
"In a move that will shake up the global auto industry, Toyota has just unveiled a water-powered engine powered by hydrogen created through electrolysis -- emitting only water vapor! No lithium. No charging stations. Just pure disruption."
This is pure nonsense, but I have been hearing similar stories for decades. I believe the first version I ever heard was that a brilliant inventor had invented a car that ran on water, but the oil companies bought the patent. Or otherwise made the man disappear.
These claims are revived every few years, so let's clear this up.
Although water can be an energy source, it is not a fuel. Water is actually the combustion product of hydrogen, which is a fuel. Water is produced when hydrogen is burned. Water can function as an energy source in some situations. Falling water can produce electricity via hydropower, and moving ocean water can produce electricity via tidal or wave power.
But water as the power source for a vehicle is nonsense. Consider the claim above. A "water-powered engine", which is immediately contradicted by the phrase "powered by hydrogen created through electrolysis." Is the latter phrase technically viable? Yes, but it misses two issues.
First, the power source--the fuel--is actually hydrogen. Energy as electricity is being put into the water to split it apart and create the hydrogen (and oxygen). In other words, hydrogen (via electricity) is the power source, but water is a power sink.
More importantly, where is the energy coming from to create the electricity for the electrolysis? In this scenario, that would likely have to come from a battery. But such a scenario would be inefficient, because each energy conversion stage involves efficiency losses. That's basic thermodynamics. Rather than use a battery to produce hydrogen via electrolysis, which then has to be converted into energy to power a car, it would be far more efficient (and practical) just to use the initial electricity directly without the conversion steps.
There's no question that Toyota has been very active in developing hydrogen vehicles.
The confusion seems to stem from a real announcement by Toyota last year. The company filed a patent for a water-cooled hydrogen combustion engine. That's a very different thing than a car that runs on water.
In Toyota's design, the engine runs on hydrogen, not water. The claimed innovation lies in the cooling system. Instead of relying on traditional radiators or air cooling, Toyota's system injects water directly into the cylinders. This helps control the high combustion temperatures associated with hydrogen and allows the use of lighter engine materials -- ultimately improving efficiency and reducing weight.
But the vehicle still requires external hydrogen refueling. It doesn't split water into hydrogen onboard, and it's not powered by water. The term "water engine" in this case refers to the cooling system, not the fuel source.
The recurring claims of a water-powered car make for great clickbait, but they don't align with the laws of physics. Water doesn't "release" energy as a fuel. It requires some other energy source to convert it into a fuel.
That doesn't mean hydrogen-powered vehicles aren't technically viable. They are, and Toyota has been a pioneer in that space. But hydrogen needs to be produced, stored, and delivered, and every step in that process consumes energy.
So no, Toyota hasn't built a car that runs on water. They just patented a potentially better way to cool a hydrogen engine. And while that may be good engineering, it's not the miracle of free energy people envision when they read and share "water-powered car" stories. The real story is more nuanced -- and far more grounded in science. It's just not as click worthy.