Biodiesel has proven itself as a technically sufficient alternative diesel fuel in the fuel market since the beginning of 1990s. Its applications in automobiles, ships, and heating systems have been accepted by both European countries and the U.S.A. Generators are crucial equipment of industry and have a wide usage area in agriculture. Also, engine performance and emissions of electric generators get very important due to their indoor applications. The objective of this study was to investigate the engine performance and smoke results of used cooking oil originated biodiesel utilization in electric generators. The engine performance and emission tests were conducted with 90-mm stroke, I cylinder, and a 9-kW 3 LD 510 coded diesel engine, and generator performance tests were performed in a generator set consisting of 90-mm stroke, 1 cylinder, 4 LD 640 code, and a 10.5-kW diesel engine and 10-kVA max output, 14.4-A current, and 400-V A 100 LB coded Rotating Field Three Phases AC Generator. Consecutive tests on No. 2 Diesel fuel, B100, and B20 were conducted, and the results were compared with each other. When compared to No. 2 Diesel fuel, both B100 (100% used cooking oil originated biodiesel) and B20 (20% used cooking oil originated biodiesel + 80% of No. 2 Diesel fuel) utilizations showed improved results on engine performance and emissions. B100 application resulted in lower smoke production than that of B20, whereas B20 resulted in higher power generation and lower brake specific fuel consumption when compared to B100. According to the result obtained, used cooking oil originated biodiesel can be utilized as a neat fuel or as a blend component during generator applications in rural areas and indoor applications.