Thanks Doug,

I did a few searches but your "heat content" was the key, I got so many
hits it was useless with the searches I did. DUH!! Slapping myself on
the forehead.

I will see if the tank is marked with "gallons."

Given the gallons though, what do I do with them and 90K/gal? I think
the tanks are around 5 gallons. I'll go look.

I need to look up exactly what BTU is, (other than British Thermal
Units ;-O), but is that rating for the heater per hour or minute or
what?

Thanks so far though.

Dave