No. Most new electric water heaters are highly efficient with respect to the amount of heat loss radiating from the storage tank. This is due to the use of “blown in” polyurethane foam insulation as the insulating method for modern tanks, compared to the fiberglass blanket style insulation used by water heater manufacturer’s largely in the past. As such there is little to no benefit, and very possibly a detrimental effect to efficiency, installing an insulation blanket on a new electric water heater constructed with foam insulation.