Shortly after departure the single-engine airplane experienced an electrical failure. The private pilot elected to return to his departure airport for landing. The pilot performed an emergency landing gear extension; however, with no electrical power remaining, he could not verify that it was down and locked via the gear position lights. Seconds after the airplane touched down to the runway, the right landing gear collapsed. Unable to maintain directional control, the airplane departed the right side of the runway and hit a runway light, before coming to rest in an upright and right wing low position alongside the runway. The airplane’s right wing spar and right aileron were substantially damaged during the accident. An examination of the right landing gear revealed that the downlock mechanism had not fully engaged, thus resulting in its collapse. In addition, the electrical failure was due to an inoperative alternator.