Looked at quite a few of these 'over unity' ideas, and it strikes me that:
All claim to give more energy out than drive the thing... BUT if that's the case why don't they do a closed loop demo, with the output PROVIDING the input? If they could do that it would be a 'Wright Brothers Moment' - a clear and incontrovertible proof that it can be done.
Instead, they invariably compare the readings of input and output DMMs and calculate wattage from that. Here lurk two massive gotchas -that power is not necessarily equal to VxI in AC circuits, and that under pulsed conditions many cheap DMMs will totally misread anyway. I suspect it is the experimenters' lack of understanding of this that leads to false conclusions.
Rossi demonstrated his E-Cat much like that, powering from mains and dumping the steam it produced down the drain after measuring the water volume and claiming that the amount boiled off could not be accounted for by the energy input. Why for heaven's sake did he not buy a small steam engine and generator and PRODUCE the input power from the steam? That would be the gold standard proof that it works. OK, steam engines are not all that efficient so there might be issues with losses being greater than gains, but I'm surprised he didn't at least try to create a closed loop.
The Bedini motor/generator is an interesting one - he claims to be able to charge one SLA battery from another through the machine, then reverse the process leaving both SLAs in a better state of charge than before. The problem I see with this is that he was (I believe) using old SLAs which were probably sulphated, and putting pulsed current through a sulphated battery will tend to rejuvenate it by breaking the (insulating) sulphate off the plates.
Thus, the 'excess energy' in this case may simply arise from the battery having been charged before it became sulphated, and the removal of the sulphate unlocking this stored energy. Just my theory but it would explain his results.