A building automation system (BAS) controller includes a power supply, a primary controller, and plurality of USB ports for connection to a set of supported peripherals. The primary controller identifies the inserted USB device type and, based on device type, estimates a current draw of the USB device. The total estimated current draw of all inserted USB devices is added to the current draw of the primary controller and compared to the available capacity of the power supply. If the combined current draw is above a threshold, any remaining USB ports in which no USB devices are inserted are deactivated, thereby preventing the use of further USB devices. In embodiments, the BAS controller includes an auxiliary peripheral device power interface, and the total current of connected auxiliary peripheral devices is included in the combined current determination. A user interface coupled to the BAS controller displays power allocation status.