We recently bought a new house that has dual 50-gallon electric water
heaters. Each heater has a single 5500 Watt heating element.

The 'problem' is that there are only two of us living in the house, and we
very likely don't need 100 gallons of hot water standing by. The electric
bill is out of control, and we're thinking the dual water heaters are a
chunk of that.

The two heaters appear to be plumbed in parallel rather than series. Can I
turn off the cold water inlet valve on one heater and unplug it to save some
electric power? Do I need to drain the heater that I won't be using? Should
I take the extra step of connecting the inlet pipe to the outlet pipe, (on
the plumbing side, not the heater side), in order to completely bypass that
heater? What else might I be missing?