Backup power systems and methods of operation thereof. In one embodiment, a backup power system constructed according to the present invention includes: (1) an enclosure, (2) an engine, having an air inlet, located within the enclosure, (3) an alternator, coupled to and driven by the engine, that converts mechanical power derived from the engine into AC electrical power and (4) a baffle, located within the enclosure and about a portion of the engine to block direct fluid communication from within the alternator to within the engine, that guides cooling air received into the enclosure sequentially through the alternator to cool the alternator, around the baffle and the engine, through the air inlet and into the engine to cool the engine and through an outlet port of the baffle, the baffle thereby establishing a serial path within the enclosure for the cooling air.