A method of operating a HVAC system in a vehicle having an engine that operates in a high efficiency mode and a less efficient mode is disclosed. The method may comprise the steps of: operating a refrigerant compressor to cool a passenger compartment and charge a cold thermal storage apparatus; determining if a cold charge in the storage apparatus has exceeded a threshold; enabling compressor cycling if the cold charge in the storage apparatus has exceeded the threshold; detecting if the engine is operating in the high efficiency mode; determining an amount of HVAC loads on the engine; determining a proximity of the engine operation to a switching point from the high efficiency mode to the less efficient mode; and conducting a HVAC load shed if the HVAC load reduction allows the engine to stay below the switching point and the compressor cycling is enabled.