The output temperature and flow output, even visually, are convincing. They are visually equivalent to putting off a candles by blowing them, that is 0.2W - 0.4W. But to make it only by heating water and vaporizing requires more than 2000KW.
I don't think the con comes from that. If that was so easy, he wouldn't be ashamed of making 3 day long presentations. Rather, I focus on the small time he takes with presentations. Notice that the only long presentation that we know, 18hours or so, was done with his friend that is always in the background in other experiments, Levi.
