James Watt developed the separate condenser that made steam engines far more efficient in 1765.
While repairing a model Newcomen steam engine, Watt realized that repeatedly heating and cooling the cylinder wasted substantial energy. His separate condenser allowed steam to condense in a different chamber, keeping the main cylinder hot and reducing fuel consumption.
Watt did not invent the steam engine itself. Thomas Newcomen had developed an earlier atmospheric engine, and Watt’s contribution was a crucial series of improvements that made steam power practical for a much wider range of industrial uses.
Watt partnered with manufacturer Matthew Boulton, and their engines became important during Britain’s Industrial Revolution. The unit of power called the watt honors James Watt.