Abstract: A building power management system is disclosed. The system includes a stationary energy storage device and a rechargeable, portable energy storage device. The stationary energy storage device includes a charging dock for receiving and charging the portable energy storage device. The stationary energy storage device can charge the portable energy storage device even when an electrical grid is unavailable. The portable energy storage device can provide power for other devices. Based at least in part on charge levels of the stationary energy storage device and the portable energy storage device, the power management system controls charging and discharging of the stationary energy storage device and the portable energy storage device.