Hello... first post here so take it easy on me. From the Book: "Aquatic Systems Engineering: Devices and How They Function, Selection Installation Operation" by P.R. Escobal In the section about heat loss (section 12.9) the author gives the basic conductivity equation in the form: Q = (A * 2.54) * k * T * time/d Where: Q = calories A = Area in square inches (using 2.54 to convert to centimeters) k = cal cm/sec in Celcius T = Temperature differential between Hot and Cold side of panel in degrees Celcius d = thickness in inches So using an example of A = 3505 square inches k = .002 (thermal conductivity of glass) T = 4.44 degress celcious (8 degrees F) t = 1 second d = .375 inches Q = 3505 * 2.54 * .002 * 4.44 * (1/.375) Q = 251.85 So far so good. The result is consistent with any other form of the conductivity equation I find. I tried a few different variation and got the same result. So here is where I am confused. The equation outputs 251.85 calories. I presume that because I chose 1 second as the TIME, then thermal loss to the aquarium is 251.84 calories/sec? 1 Watt = 4.184 calories/sec So 251.84 calories/sec = ~1054 Watts HOWEVER: The author indicates that to convert the result to Watts, you must multiply Q by 0.23889, giving a result of 60.16 Watts! If I use the conductivity equation in the form found here: http://hyperphysics.phy-astr.gsu.edu/Hbase/thermo/heatcond.html I get the result of 1055.5 Watts or 3601.62 btu/h There is no "time" input. I would assume that it is an HOUR based on the BTU/h form fields. That exactly matches the results from the authors equation before his conversion to Watts. What am I missing here? Where is the authors multiplier to get Watts coming from? Oddly, if I divide the BTU/h result by 60 I get the authors Wattage number. But I don't understand where the factor of 60 is coming from. The authors equation is in calories/sec and the reference equation from the website is in btu/h both give the same answer that is a factor of 60 from the authors Wattage. Somebody please enlighten me!