A piston internal combustion engine with generator has two cylinders and cylinder heads and pistons with connecting rods and two crankshafts which are connected by gears with a ratio of 1:−1 (with opposite direction of rotation). The first crankshaft with the gear is mounted parallel to the second crankshaft with the second gear in one engine case such, that the gears engage. The first crankshaft is coupled to the first generator rotor and the second crankshaft is coupled to the second generator rotor or the flywheel. The moment of inertia of the first crankshaft assembly with the first gear and the first generator rotor is equal to the moment of inertia of the second crankshaft assembly with the second gear and the second generator rotor or flywheel. The cylinders with the pistons and are positioned perpendicularly to the plane of symmetry between the crankshafts, with the axes of the pair of cylinders lying in a plane with the both pistons being at the top dead center simultaneously.