I agree with you, but I cannot easily convert my pots to electric and compare directly.
I can calculate how long it takes me to heat water and how many lbs of propane I use, but the comparison to electric would not be a fair one unless the efficiency number also had vessel loss in it, which 100% obviously does not.
I see your point. That throws another wrench into it. What are you boiling in? Stainless compared to other metals is relatively non-conductive...Another reason direct fired vessels may be less effecient.
I have heated water in my uninsulated (covered) HLT to 125, left it at about 50 degree ambient temps for over 12 hours and come back to 85 degree water. So, if we are talking similar vessels, the heat loss from the vessel itself should be negligible at least for our purposes.
Also, we agree that electric cannot be assumed at 100% There are losses between the meter and element. If we figure electric at 95% we can at least get some comparison.