The present disclosure envisages a building management system for a building. The building management system includes a building controller, a power over Ethernet (PoE) adapter, and a PoE source. The building controller is configured to operate one or more building equipment of the building, wherein the building controller is powered via alternating current (AC) power. The power over Ethernet (PoE) adapter comprises one or more circuits configured to receive PoE from the PoE source, wherein the PoE source is configured to generate the PoE having direct current (DC) power. Further, the PoE adapter is configured to generate AC power based on the PoE received from the PoE source, and provide the AC power to the building controller.