How do heat pump HVAC systems improve EV efficiency compared to resistive heating?

Heat pumps move heat rather than generating it, achieving 2-4x more heating per unit of electricity (COP 2-4) compared to resistive heating (COP = 1). They extract heat from outside air even at low temperatures, or recover waste heat from motor/inverter. This significantly reduces winter range loss - from 30-40% with resistive heating to 15-20% with heat pumps. Challenges include performance degradation at very low temperatures (below -10C) requiring supplemental resistive heating, added complexity, and refrigerant management in crashes.