Heating in Henan should not be a problem, but it is best to add an auxiliary electric heater in reserve, the coldest days on the open for a while.
Heat pump water heater thermal efficiency is indeed higher than the electric water heater 4 times, but it must be borne in mind that the heat pump water heater energy efficiency ratio is with the temperature changes, the machine on the nominal heating capacity is generally measured at 7 degrees ambient temperature, when the temperature to 0 degrees, the heating capacity of up to half of the remaining, that is, the thermal efficiency of the change from 4 to 2, to minus 5 degrees is the same as the electric water heater, plus the frost power consumption. The overall thermal efficiency is not as good as an electric water heater at that point in time.
Whether something is energy efficient or not, it is under certain conditions. You can't just publicize the advantages in order to sell the product.