We've had a tankless water heater for years although ours is gas. One of the pluses is it gives you unlimited hot water which matters more if you like to take long showers or have several people wanting to shower close together. There are too many variables (cost of a particular water heater, price you pay for electricity) to know how long it would take you to make back what you pay for the heater. I'd think with all your travel you'd save more than average since you wouldn't be using electricity to heat water while you are out of town.