​19th Century: The Birth of Dedicated Water Heaters

In 1868, Benjamin Waddy Maughan, a London painter, patented the first gas instantaneous domestic water heater that did not use solid fuel. Named the “Geyser,” cold water flowed through pipes heated by a gas burner at the base. The design had no flue to remove combustion gases and was therefore dangerous, yet it established the principle of on-demand (tankless) heating.

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1889–1890 Edwin Ruud, a Norwegian-American mechanical engineer working in Pittsburgh for the Fuel Gas and Manufacturing Company (associated with George Westinghouse), designs and patents the first automatic storage-tank gas water heater.

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• Design completed in 1889

• U.S. Patent 443,797 granted 30 December 1890

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The unit used a bottom gas burner controlled by a temperature-sensitive valve — the foundation of the modern automatic storage water heater.

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1891 Clarence M. Kemp of Baltimore patents the Climax, the first commercial solar water heater (U.S. Patent 451,384, 28 April 1891). Black tanks enclosed in a glass-covered, insulated box heated water using solar energy. The system sold especially well in Southern California; by the late 1890s, roughly one-third of homes in Pasadena used solar water heating.

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1897–1898 Edwin Ruud leaves the Fuel Gas company, founds Ruud Manufacturing, and patents an improved automatic instantaneous (coil-type) water heater (U.S. Patent 610,281, 6 September 1898). This design used a copper coil inside a cast-iron shell with thermostatic gas control. Ruud popularized both storage and instantaneous automatic heaters and remained a major manufacturer for decades (later under Rheem).

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1909–1910 William J. Bailey patents the Day and Night solar water heater. The critical innovation was separating the outdoor flat-plate collector from an insulated indoor storage tank, allowing hot water day and night via thermosyphon circulation. Thousands were installed in California; rights were later transferred to Florida, where solar water heating became widespread until cheap natural gas displaced it.

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1900–1945: Electrification, Mass Production Foundations, and War

1924–1927: Dr. Theodor Stiebel founded ELTRON in Berlin and developed the coil immersion heater (1924). In 1927, the company produced its first small instantaneous electric water heater — an early commercial electric tankless design. Stiebel Eltron would become a major force in electric water heating.

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1930–1931 Rheem enters the automatic gas storage water heater market. By 1941, the company is the largest U.S. manufacturer of automatic water heaters.

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1936 A.O. Smith patents a process for glass-lining steel tanks (adapted from its brewery-tank technology developed during the Depression). Glass lining dramatically improves corrosion resistance and makes reliable, affordable storage tanks practical for average households.

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1939 A.O. Smith begins mass production of residential glass-lined water heaters. Production is interrupted by World War II, during which the company manufactures bombs, aircraft components, and military water heaters.

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1946 State Water Heaters is founded in Nashville by Herbert Lindahl Sr. The company later pioneers foam insulation between the tank and jacket (late 1970s) and is acquired by A.O. Smith in 2001.

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1948 A.O. Smith acquires the Burkay Company, entering the commercial instantaneous and coil-type market. The first glass-lined commercial water heater (Burkay B-65) appeared in the early 1950s.

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Post-War Expansion (1945–1980s)

Late 1940s–1950s Post-war housing boom and expanding gas and electric utility networks drive rapid adoption of automatic storage water heaters. Glass lining becomes the industry standard. Monthly production at major plants reaches tens of thousands of units.

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1950s–1960: Continued refinement of thermostats, immersion elements, anode rods, and safety controls. Electric storage heaters become practical in more regions as electrical infrastructure improves.

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1970s Energy Crises: Rising energy costs spur interest in efficiency. Foam insulation reduces standby heat loss. Early modern tankless systems gain attention in Europe and Japan; U.S. interest begins to grow.

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In the late 1970s, State Water Heaters pioneered the use of polyurethane foam insulation between the tank and outer jacket, a major improvement over earlier fiberglass methods.

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Efficiency Era & Modern Systems (1987–Present)

1987 National Appliance Energy Conservation Act (NAECA) establishes the first federal minimum efficiency standards for residential water heaters in the United States (effective approximately 1990). Subsequent DOE rulemakings progressively raise requirements.

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1990s–2000s Modern gas tankless water heaters, refined by Japanese manufacturers (notably Rinnai and others), enter the U.S. market in greater numbers. Condensing technology, digital controls, and better reliability drive adoption. Energy efficiency and unlimited hot water become primary selling points.

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In 2009, ENERGY STAR began certifying heat-pump water heaters. These units, which move heat rather than generate it directly, achieve coefficients of performance typically between 2 and 4.

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2010s–2020s

• Continued tightening of DOE efficiency standards (including the 2015 update that effectively pushed larger electric storage units toward heat-pump technology).

• Growth of hybrid heat-pump water heaters with electric resistance backup.

• Condensing tankless systems are becoming more common.

• Integration of recirculation, smart controls, and improved scale resistance for hard-water regions.

• Ongoing research into further efficiency gains, materials, and grid-interactive systems.

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Notes on Sources & Accuracy

Dates and attributions on this timeline are drawn from patent records (USPTO and historical British patents), manufacturer histories, contemporary engineering literature, and museum collections. Common online discrepancies (especially around Ruud’s 1889 design versus 1890 patent) have been resolved in favor of primary documentation.

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This timeline is updated as new verified research becomes available.