In 1923, an experimental mercury boiler turbine invented by General Electric began generating about 1,500 kW of electricity at the Hartford Electric Light Company's Dutch Point Station*. It was claimed to be more fuel efficient than steam turbines alone. Boiling mercury (354ºC) needed a smaller fraction of the total heat input than for vaporizing water, and it operated at lower pressure causing less stresses in the pipes. After the mercury vapour drove the first stage of turbines, the exhaust heat from the mercury was used to produce steam for a second stage of steam turbines. By 1947, three full-scale plants had been built, but later conventional steam plant efficiency exceeded the mercury/steam cycle, so the toxic design was abandoned.«[Image: schematic of the mercury and steam circuits for generator.]