Thomas Clarke wrote: "I think you'd better question that. COP < 1 is a physical impossibility without some (presumably nuclear, given the large accumulated energy deficit) endothermic reaction in Rossi's reactor..."
As I made clear previously, I mean the COP in the fluid. In HVAC applications they measure the COP of the hot water or steam, not the entire system. Heat losses from the boiler walls are not included.
A scientist with a calorimeter might try to estimate losses. That is, heat not captured by the flow of cooling fluid in a mass-flow calorimeter.
Rossi's device is a suboptimal electric boiler.