Electric water heaters have no insulation in the bottom and fairly poor insulation overall. I always construct a well insulated enclosure on all six sides. The standby losses are too substantual to ignore otherwise.

This does not move the efficiency up to the instant type by any stretch. Yet does help quite a bit. I try for about R30 overall above what is on the water heater from the manufacturer.

Electricity is 11-12 cents per killowatt hour here.
It is 5.5 to 6 cents during low demand hours and all weekend.

That is if you install an electric heating storage unit for three thousand dollars and sign up. It of course only stores heat in the ceramic blocks during off hours. Larger electric water heater on a timer to try heating most hot water on low cost time helps as well.