A power consumption reducing apparatus (30, 80), which is provided in an indoor unit and/or an outdoor unit of an air conditioner, comprising: a main circuit (30a, 80a) configured to be electrically connected with an external power source to be supplied with power from the external power source, and including a main power source (41, 85) and a first direct current voltage generating section; an auxiliary circuit (30b, 80b) configured to be electrically connected with the external power source to be supplied with power from the external power source, and including an auxiliary power source (43, 87); a first switch section (51, 51') connected in series with the main circuit between the external power source and the main circuit, and configured to be able to cut off the supply of power from the external power source to the main circuit; and a switch control section (60, 90) configured to be electrically connected with the auxiliary power source to be supplied with power from the auxiliary power source, and control switching of the first switch section, wherein, the main circuit is provided with a main circuit installation device (301, 801) configured to be operated by power which is supplied from the first direct current voltage generating section or the main power source, and the switch control section is configured to switch the first switch section so that power is supplied to the main circuit during an operation mode where the main circuit installation device is being operated and so that the supply of power to the main circuit is cut off during a standby mode where operation of the main circuit installation device is stopped; characterized in that the main circuit installation device includes a voltage detecting section configured to detect a voltage which is supplied from the external power source, and a drive signal generating section configured to generate a drive signal (SU, SV, SW) for driving an actuator based on the detection results from the voltage detecting section, the actuator is a motor which is at least one drive source for a plurality of devices included in an air conditioner, the drive signal generating section includes a determining section configured to perform control to determine the drive signal using the detection results from the voltage detecting section, and an output section configured to generate the drive signal determined by the determining section and outputs the drive signal to the actuator. a main circuit (30a, 80a) configured to be electrically connected with an external power source to be supplied with power from the external power source, and including a main power source (41, 85) and a first direct current voltage generating section; an auxiliary circuit (30b, 80b) configured to be electrically connected with the external power source to be supplied with power from the external power source, and including an auxiliary power source (43, 87); a first switch section (51, 51') connected in series with the main circuit between the external power source and the main circuit, and configured to be able to cut off the supply of power from the external power source to the main circuit; and a switch control section (60, 90) configured to be electrically connected with the auxiliary power source to be supplied with power from the auxiliary power source, and control switching of the first switch section, wherein, the main circuit is provided with a main circuit installation device (301, 801) configured to be operated by power which is supplied from the first direct current voltage generating section or the main power source, and the switch control section is configured to switch the first switch section so that power is supplied to the main circuit during an operation mode where the main circuit installation device is being operated and so that the supply of power to the main circuit is cut off during a standby mode where operation of the main circuit installation device is stopped; characterized in that the main circuit installation device includes a voltage detecting section configured to detect a voltage which is supplied from the external power source, and a drive signal generating section configured to generate a drive signal (SU, SV, SW) for driving an actuator based on the detection results from the voltage detecting section, a voltage detecting section configured to detect a voltage which is supplied from the external power source, and a drive signal generating section configured to generate a drive signal (SU, SV, SW) for driving an actuator based on the detection results from the voltage detecting section, the actuator is a motor which is at least one drive source for a plurality of devices included in an air conditioner, the drive signal generating section includes a determining section configured to perform control to determine the drive signal using the detection results from the voltage detecting section, and an output section configured to generate the drive signal determined by the determining section and outputs the drive signal to the actuator. a determining section configured to perform control to determine the drive signal using the detection results from the voltage detecting section, and an output section configured to generate the drive signal determined by the determining section and outputs the drive signal to the actuator.