The present disclosure provides an HVAC system for a vehicle having a first heat source and comprising a primary loop through which a coolant circulates and a secondary loop through which refrigerantcirculates. The primary loop having two parallel sub-loops, namely a first sub-loop and a second sub-loop in which the coolant may circulate. The first sub-loop of the primary loop includes the firstheat source, a second heat source, and a first heat exchanger. The first sub-loop may partially extend into a case of the HVAC system to place the first heat exchanger adjacent an air heater. The second sub-loop of the primary loop includes the first heat source, the second heat source, and a second heat exchanger. The HVAC system having a plurality of operation modes for efficiently conditioningair in a cabin of the vehicle.