Vehicle air conditioner that operates during engine stops

A vehicle air conditioner (15) allows storing cold thermal energy in a cold thermal energy storage unit (40) during operation of a vehicle engine (4) to be used later during an eco-run mode of a hybrid vehicle. Vehicle cabin air is cooled by the cold thermal energy quantity of a cold thermal energy storage unit (40) when the vehicle engine (4) is stopped and cold air continues to be requested by passengers. During engine (4) operation, the cold thermal energy storage time, which is the time it takes for the temperature of the cold thermal energy storage unit (40) to reach the solidifying point of the cold thermal energy storage material (44) or lower, is measured. The stored cold thermal energy quantity of the cold thermal energy storage material (44) during the operation of the vehicle engine (4) is calculated based on information including the cold thermal energy storage time and cold air volumes.