Just an fyi for those wanting an inside switch for your electric side of your Hw heater and not wanting to run wires I have found a simple on / off rf transmitting remote control.
This unit is good up to 10 amps and can be wired in to remotely turn electrical portion of Hw heater on and off.
I have an inside switch so have no need to install.
Running the numbers appears that this unit is capable of the function.
Since I have not tested or installed on mine it's user beware.