Read the above everyone, remember a "Heatpump" is an AC system that transfers heat into the cabin instead of out of the cabin by changing the flow of refrigerant.
One point that might have been brought up already, there is waste heat from the Motors/Inverter and Battery that the Heatpump will use to assist in transferring heat to the cabin instead of just using the outside air.
This is the key and is a HUGE advantage, especially after supercharging in the cold.