Assuming that this device indeed features output>input electric power thing, there are a few things that need be considered as reason.
Firstly, we have to remember and accept that the second rule of thermodynamics is not always applicable. Clearly something can come out of nothing, as the whole existence of the universe blatantly tells us. The 2nd law is supposed to be true in the universe, but it's only applicable after the universe was formed, presumably in so called "Big Bang". Some people talk about creation, but the way the universe was born does not really matter. The point is that if t = time, then
t < 0 - 2nd law of thermodynamics non-applicable*
t = 0 - 2:nd law still not applicable **
t > 0 - 2nd law apparently applicable ***
...presuming that the universe was born at t = 0.
*because time before zero wasn't defined because there was nothing to measure the rate of events, thus there was no time axis yet.
**energy is borne out of (presumably) some kind of quantum balance disruption of Empty, or something similar.
***meaning that as of yet, there hasn't been measurable exceptions to rule. Though that's not actually true, quantum fluctuations of the vacuum happen all the time, they just happen in very very small scale, but they still can create measurable effects.
For example, two metal plates placed VERY near each other are pulled towards each other, because there's more fluctuation going on on the outsides than on the inside. That's very vague explanation, I know, but it gets very complex and it's called the Casimir effect. So the vacuum itself causes a force between two objects... Interesting, eh? The problem with Casimir effect is that it's a bilinear, static force, and static forces are not known of being very helpful in energy production. Gravity also generates a force, but you can't make energy out of gravity force, you can just store energy onto objects as gravitational potential energy.
Now, if the 2:nd rule can be broken after t = 0, it basically can mean some things.
Thers's basically two possibilities for the origins of the energy (if it exists): Either the energy is created in the process or it comes from *somewhere*. That somewhere is either this verse or some other verse in the multiversum.
1. The device somehow creates similar conditions to Time Zero, thus enabling energy being born out of nothingness. This possibility
There are many things that are against the possibility of a device creating similar conditions to Time Zero. Though we don't know how it actually was at that time, we only know what the conditions were few microseconds AFTER Time Zero. It's possible, but quite unprobable.
2. A second possibility is that the multiversum hypothesis is true, and somehow the device creates conditions where energy is allowed to flow from universe to other. Of course, in this case we have to stop calling our universe an universe, it'll just be a verse and the multiverse becomes the universe, because one of the definitions of universe is that it's everything there is and there's no outside...
This is actually quite interesting, but morally problematic possibility. What if we bleed some other verse out of energy? Can someone do the same to us?
If they can do the same to us, theoretically this device could be used to send messages between universes... I take three bursts of energy, they take a certain amount of bursts... soon you could do Morse with them, if the leeching point happens to be in a place where there are sentient beings capable of wondering why their powerplant output has inexplicably reduced...
3. There's also a chance that energy comes from somewhere within our own universe, by means that are not yet known (yes it's a wide shot, but much more likely than possibilities 1 and 2). Though this is not as inspiring as the earlier ones, it might create new branches of research and possibly new ways for energy transfer. Note that this possibility also contains the dreaded "Goddidit"- possibility.
Of course, that's just presuming that the device indeed works as claimed - a pretty big assume.
More likely the source of energy could be misinterpreted measurements, like different scales or even systematic measurement error that hasn't been noticed. Even NASA scientists messed up with Newtons and pounds as units of thrust with one of their more unlucky Mars probes. Or the manufacturers of the probe's computer did. Depends of the interpretation. Most likely there is some simple explanation for this, but if there isn't, then there are exciting times ahead. Who knows, it might be genuine after all.