Gas engines that run on natural gas typically have a thermal efficiency between 35-45% (LHV basis)., As of year 2018, the best engines can achieve a thermal efficiency up to 50% (LHV basis). These gas engines are usually medium-speed engines Bergen Engines Fuel energy arises at the output shaft, the remainder appears as waste heat. Large engines are more efficient than small engines. Gas engines running on biogas typically have a slightly lower efficiency (~1-2%) and syngas reduces the efficiency further still. GE Jenbacher's recent J624 engine is the world's first high efficiency methane-fueled 24-cylinder gas engine.