Do Online Hydrogen Generators Really Work?


Hi John,

What is your opinion on hydrogen generators for cars? (The ones that are available on the internet.) I enjoy your talkback program on Brisbane Radio 4BC.

Thank you, 



Hi Ed,

Thanks for listening on Radio 4BC mate.

The short answer is: they're absolutely useless.

Here's the longer version.


You can use electricity to electrolyze water. That process, called electrolysis, is well documented and it works. Water splits into hydrogen gas and oxygen gas as a result of the electrical energy pumped into it. Typically an electrolyte is added to make the water more conductive.

If you trap the gas that bubbles up (a mixture of hydrogen and oxygen gas) then you can suck it into an internal combustion engine and burn it. It re-combines as water, and energy is produced. Steam comes out the tailpipe (in addition to the other combustion byproducts from the petrol, and a truckload of nitrogen gas).


The sellers of these units say it increases efficiency and saves you fuel/money. In reality, however:

  • It won't save you any money. 
  • It won't save you any fuel.

These claims use pseudo-science to convince untrained people that the process works, but it's a kind of thermodynamic fraud.

Here's the kind of unmitigated rubbish they claim. Physicists and engineers everywhere on earth reach for the sick bag when they read this BS.

It's the modern-day equivalent of snake oil. And about as effective.

It's the modern-day equivalent of snake oil. And about as effective.

It can't work. As in - not possible. It cannot save fuel or money. Here's why:

It takes energy to split the water into hydrogen and oxygen in the hydrogen generator. That energy comes from the battery. Before that, it came from the alternator. And before that, it came from the engine. Originally, it came from the fuel.

In other words, the vehicle burns the fuel to run the engine, then the engine runs the alternator, which charges the battery, which powers the generator.

Chemical energy in the fuel turns into rotating kinetic energy in the alternator, which turns into electrical energy in the battery, which turns into chemical energy in the hydrogen generator.

There is an inconvenient truth in physics that energy can't be created out of nothing - you can't get more out of a system than you put into it. That is a universal truth - as in, it applies everywhere in the universe.

So, if the hydrogen-generation process ran with 100 per cent efficiency, the energy you get from the hydrogen would be exactly equal to the energy you put into the process (in the fuel to run the engine to make the electricity to split the water up into its component gasses).

So, the best-case scenario is: no benefit whatsoever.

Unfortunately, no processes in the real world is totally efficient. You lose a lot of energy in the fuel through inefficiencies in the engine (it take a lot of energy to compress the next fuel/air charge on the way into the chamber) plus there is frictional losses and unused energy in the hot gasses as they exit the exhaust port. Conversion of the rotational energy of the engine into electricity is hardly efficient either. Neither is electrolyzing the water (there's a lot of resistance in the hydrogen generator).

The vast majority of the energy in the fuel that is originally burnt to convert the water into hydrogen is inevitably lost to the environment. So the energy in the hydrogen produced is vastly less than the energy in the fuel used to make it. This is fundamentally why these systems are a con. There's no clever way to subvert this fact with technology.

A Reality Check

Every day around the world, thousands of engineers and technicians go into engine development labs in car maker's R&D centres. Their job is to make engines more fuel efficient. Fuel economy is an unbelievably big deal in the automotive industry. Fuel efficiency sells cars, and it is needed to meet tighter regulatory requirements as well.

The systems being developed are expensive - direct injection, engine auto stop/start, low rolling resistance tyres, low-friction ancilliary drive systems, cylinder deactivation, etc. These things cost HEAPS to produce. 

If it were as simple as putting a hydrogen generator under the bonnet, which could be done at very little cost, every car maker on earth would have done it already. 

They don't - because these things just don't work.


Hydrogen gas is highly flammable. In confined environments there's a significant explosion risk. I wouldn't be plumbing a hydrogen generator under the bonnet because:

  1. It won't work. (Here 'work' means 'save you money'. It will generate hydrogen and oxygen gasses.)
  2. It could easily burn the car down or blow you up.

Check this third-party YouTube video on DIY hydrogen generators, and how powerful the explosive potential is.

In short, in-car aftermarket hydrogen generation systems are a dangerous fraud.

If you want to save 15 per cent on fuel, pump up your tyres and drive more conservatively.

Sorry - probably not what you wanted to hear.