1–10%. However, with the addition of a condenser, Corliss valves, multiple expansion, and high steam pressure/temperature, it may be greatly improved. Historically into the range of 10–20%, and very rarely slightly higher. A modern, large electrical power station (producing several hundred megawatts of electrical output) with steam reheat, economizer etc. will achieve efficiency in the mid 40% range, with the most efficient units approaching 50% thermal efficiency. It is also possible to capture the waste heat using cogeneration in which the waste heat is used for heating a lower boiling point working fluid or as a heat source for district heating via saturated low-pressure steam. See also Notes References References Further reading Rose, Joshua. (1887, reprint 2003) Modern Steam Engines Van Riemsdijk, J.T. (1980) Pictorial History of Steam Power. (lecture) External links Animated engines – Illustrates a variety of engines Howstuffworks – "How Steam Engines Work" Video of the 1900 steam engine aboard paddle steamer Unterwalden 18th-century inventions Energy conversion English inventions Gas technologies Piston engines