“What the hell is “10KW” of heat?”
Since one watt is equal to 3.41442595 BTU’s you should be able to do the math.
Ok, so they claim they get 30,000 BTU out of 400 watts of power. Here again is a complete line of B.S. You failed to consider Resistance, Voltage and several other factors that determine the amount of heat electricity can produce. That always varies and is completely dependent on those other factors.
Your “math” is quite “fuzzy”!( At a ratio of 400 to 1.)