Australian energy company Lavo is throwing down the gauntlet to Tesla’s Powerwall with a home battery storage system that doesn’t rely on conventional batteries at all, opting for hydrogen as fuel instead.

Lavo’s battery, which it’s calling the Green Energy Storage System, works by pulling in water and using electrolyzers to separate it into its constituent atoms, hydrogen and oxygen. The system then stores the hydrogen, in its solid state, in the silver tanks. (Lavo’s proprietary metal hydride powder captures the hydrogen in the tanks.) Users can then run the hydrogen back through a fuel cell in order to generate electricity, much like a hydrogen vehicle.

Thanks to its massive 40 kilowatt-hours capacity, Lavo’s battery has nearly three times the capacity of Tesla’s current-gen Powerwall 2. That is plenty of energy to power an average home for two days straight and a strident shot across the industry’s bow.

Lavo says the key bits of the battery system last up to 30 years instead of maybe 15 from a lithium battery thanks to its reliance on hydrogen gas rather than the chemicals in a conventional battery. It is technically more environmentally friendly as it doesn’t use as many rare earth metals. There are also no toxic chemicals to dispose of afterwards, and the company says that even though it’s a bit of a beast, a single Lavo system is more compact than an equivalent amount of battery storage.

But then there’s also the chance of fire or in the very worst case a Hindenburg-like explosion. Lavo says any leaks will disperse quickly, though, making it “inherently no more dangerous than other conventional fuels such as gasoline or natural gas,” as the company writes in its FAQ.

On the downside, there’s the efficiency. Batteries store and release energy with minimal losses; for every kilowatt-hour your rooftop array generates and sticks into a battery, you’ll get back more than 90 percent of it. But the process of generating hydrogen by electrolysis using a proton exchange membrane is only about 80 percent efficient, so you lose 20 percent straight away. And at the other end, you’ll lose somewhere around half of what you’ve got stored in the process of converting the hydrogen back into energy through a fuel cell.

So not only does it take more energy to fill up, a 40-kWh hydrogen energy storage system might start looking a lot like a 20-kWh system when you actually try to get the energy back out of it. The Lavo folks say this system’s “round-trip efficiency is above 50 percent,” so taking them at their word, you’re still tossing out roughly as much energy as you’re keeping.