This was marvelous:
E. Beiting, “Investigation of the nickel-hydrogen anomalous heat effect,” Aerospace Report No. ATR-2017-01760, The Aerospace Corporation, El Segundo CA, USA, May 15, 2017.
The problem with thermal-to-thermal claims of COP > 1 is that if they were real, it would be easy to make them self-sustain, because the nasty Carnot efficiency limit is not there. (The Carnot limit provides the excuse for not closing the loop in electrolysis experiments.)
Beiting uses the old small-amount-of-fuel trick so popular in cold fusion research, so that a small artifact can be plausibly mistaken for heat from nuclear reactions -- that is, plausible to those who have consumed the kool-aid.
If his fuel were producing a watt of power from nuclear reactions, then 20 times that amount of fuel at the same temperature would produce 20 watts. Now, the fuel could be sufficiently insulated so that 20 W maintained the required temperature, and so once started, the input could be turned off.
When he's done that, the world will beat a path to his door. As always, I'm not holding my breath.