A GUI is available to look up the efficiency of any water heater,
residential or commercial at http://www.gamapower.org

For example, residential hot water heater efficiency can be obtained at
http://www.gamapower.org/water.php

What a poorly designed page! I gave up. Most annoying is each time you
return to the page to make a change it clears all your input away and you
have to reinput everything.

And it does not seem to include the model GPHE-50 (AO Smith Vertex) that I
just had installed.

Go to link - PDF file - pg. 15 (document page 217) 4th entry down for A.O.
Smith
http://www.gamanet.org/gama/inforesources.nsf/vAttachmentLaunch/BD9C57BA8477D8E185256E9000606CD0/$FILE/12-07-gas-cwh.pdf

Also:
http://www.saskenergy.com/saving_ene...terHeaters.pdf