Does an electric water heater have to be 18" high as a gas one does
This is a tricky question and a gray area in the codes. Much discussed in the Inspection forums. The code refers to an "ignition source" needing to be 18 inches off the floor.
Obvious for a gas heater but not so obvious for an electric unit. It could be argued that a making and breaking electrical contact, subject to sparking is an ignition source. I would agree. On the other hand, the thermostat where this would occur is located pretty high up inside a closed compartment in the units I have installed.
Of course, this only applies to water heaters installed in a garage where there is a potential for gasoline leakage and the resultant combustible fumes.
Ultimately, it depends on your local code enforcement authority and how they interpret what ever code they are following. Overall, the general consensus is yes, illogical as that may seem. Go Figure! Your mileage may vary. LOL