This paper describes a smart office energy management system (SOEMS) that can reduce the energy consumption of PCs, monitors, and lights in an office environment through the use of a mobile app and Bluetooth Low Energy based Beacons (BLE Beacons). BLE Beacons placed at several places in an office and a mobile app are used to determine whether a user enters or exits the office to change the power saving mode of the user's PCs, monitors, and lights. The proposed system can reduce energy consumption in the office without causing user inconvenience.