I don't know exact numbers, but heating water with electricity is the most inefficient method. The recovery rate is very
slow, I can say with 100% certainly you will run out of hot water on a regular basis with an electric HW heater. I switched from electric to an Aero oil-fired in 2002. Huge difference. At the time my electric bill dropped $50/month.
Also, if there is any Calcium Carbonate (hardness) in the water the tank with begin to accumulate deposits on the elements which will slowly fall off and begin filling the tank. Once the lower element is covered it's good bye. I had the electric unit before I installed a water softener, every few months I had to drain the tank, clean the elements, and stick a thin pipe into the tank through the element mounting point to try to suck out the deposits with my shop vac.
There's a long run from the heater to the kitchen sink, I do have a 5 gal. electric heater under the sink connected to the hot water line which provides instant hot water at the faucet. It doesn't operate very much since hot water feeds it. That's about as far as I will go heating DHW with electricity.
My vote is to heat DHW with coal, either 100% or with a loop or coil in a coal stove/boiler.