The disclosure is for a capacitor cooled by a heat pipe. The capacitor casing is constructed with an open tube inserted through the casing wall and into which is inserted a simple cylindrical heat pipe. The heat pipe may terminate at the casing wall which then acts as a heat transfer surface, or a portion of the heat pipe which extends beyond the end of the capacitor can be attached to an external heat transfer device, such as a heat conductive mounting plate or a cooling fin assembly.