Compressor output calculation unit and control unit using the same

A compressor output calculation unit having a variable displacement compressor, a condenser, a pressure reducing mechanism and an evaporator, wherein a compressor torque or power is calculated based on a detected or estimated value of a refrigerant flow rate, a detected or estimated value of a refrigerant discharge pressure, a detected or estimated value of a refrigerant suction pressure, and a compressor rotational speed, and a control unit using the same. The compressor torque or power may be estimated at a high accuracy without using a refrigerant flow sensor.