The Unitary HPAC (Heat Pump Air Conditioner) System has been developed to enable a heat pump system in passenger vehicles. Unitary HPAC uses technology of reversing the coolant instead of refrigerant to distribute heat from where it is generated to where it is needed. Integrating this system in a plug-in hybrid vehicle reduces the energy required by the heating and air conditioning system, reducing the grams of CO₂ per mile by up to 25%.Although this system can be applied to any passenger vehicle, it is most beneficial to hybrid and electric vehicles, because it provides an additional source of hot coolant. These vehicles provide less waste heat than conventional internal combustion engine vehicles so they must rely on electric heaters to provide the heat needed for comfort. The electric heaters are an energy draw that reduces the electric drive range. The Unitary HPAC system will extend the electric range significantly. In addition to maintaining passenger comfort in cooling mode, heat can be removed from the battery, inverter, and electronics with coolant and directed to the passenger compartment.This paper will use a plug-in hybrid vehicle to demonstrate the operation of the Unitary HPAC. It will show how the Unitary HPAC can significantly reduce refrigerant charge and provide passenger comfort with less energy.