Originally Posted by goneriding
It would only take 30 amps, I don't know what barn wouldn't handle that, a lot have 220 volts 100 amps ran to the barn. Haven't heard of a barn only having 110.
A small tankless water heater requires about 60 amps, but unless you're in an area where the incoming water temperature is high enough, the smaller models won't heat sufficiently - you need a larger more capable unit, and they can easily draw up to 150+ amps. The last electric on demand heater I saw for sale up here required three 60 amp circuits at 220v. 180 amps. Not many barns I know of are wired for 180 amps at 220v.
These ridiculously high power demands are why most tankless systems up here are natural gas.