FWIW, I have measured my incoming water in the winter after a cold spell of 33-degrees F. Most people want the outgoing water for a shower at about 105-degrees, and it generally loses at least some on the way to the shower, plus, you'd probably want to mix in at least a little cold...this can give you an idea of the temp rise, in my case it could be 80 or more (the dish washer is pretty useless without it being MUCH hotter unless it has internal heaters to condition the water - some do, some don't). It takes a LOT of power that is MUCH easier to achieve with NG verses electric given most people's panel.
Other than a point of use water heater, most electrical tankless systems are inadequate in many locations because of both the available power and the temperature rise at a volume that makes taking a shower or filling a tub viable