It takes at least as much energy to break water down into hydrogen and oxygen as is released when hydrogen and oxygen are recombined back into water (burned).
If it didn’t it would be perpetual motion.
It is as simple as that.
On their website they say....
‘On input of 500 watts the mini reactor produces a output of 2,797 cu feet of hydrogen per hour. (electricity equivalent of 221.5 KWH at a cost of about $1.80)”