Install a shut-off valve on each line between the heat pump and the water heater tank. Supply back-up heating, if necessary. In a retrofit situation, you can usually leave the electric heating coils and thermostats in the storage tank intact. When the heat pump alone can't satisfy the temperature setting, the electric elements will. If back-up heating is unnecessary, disconnect the heating coils.
Many commercial buildings use air conditioning almost year round.
For example, a restaurant produces so much heat that even when it is cold outside, the building may need cooling. A heat pump water heater can provide additional cooling at the same time as it is heating water.