I can not give you all the temp and gauge info.. such as flue temp.. I have yet to get a flue therm. However... I am just curious as to a general idea... a range. I have the Tarm 40 Solo Plus. Install this year. It has been fun learning about it.. and of course using it.. savings are great and the hot water is awesome... with 3 athletic kids who shower all the time. Anyways... what kind of efficienceis am i getting? I know the top can be near 87.... but what is my low? What is the lowest rating if alot of things are at the low end of spectrum? LIke heat exchange tubes are dusty... and wood is not great. Not that I have this problem.. I was just curious ... to see. Kind of like... no one ever tells you what your oil boiler is rated at when it is dirty... they always tell you after cleaning it is at 83 or 85.... BUt they never say... well.. BEFORE i cleaned it you were running at 75 efficient. ANy thoughts?