The U.S. Patent Office granted Ida R. Forbes Patent No. 1,258,441 for a thermostatically controlled electric water heater, described in French sources as an early domestic electric water-heating device.
On March 5, 1918, the United States Patent Office formally granted Ida R. Forbes U.S. Patent No. 1,258,441 for her invention, the 'Electric Water Heater.' The patent covered a thermostatically regulated apparatus capable of heating water to a set, controlled temperature using electric heating elements, a notable engineering achievement in the still-nascent field of household electrification.
French-language secondary sources have since described this invention as among the first devices to apply electricity specifically to domestic water heating, situating Forbes within the broader history of technological innovation that transformed everyday home life in the early 20th century. While definitive verification of an absolute 'world first' claim has not been established through primary sources, the patent stands as clear documentary evidence of Forbes's contribution to the emerging field of electric home appliances.
Being awarded a patent in 1918 was a notable achievement for any inventor, but particularly significant for a woman working in a mechanical and electrical engineering context, fields in which women inventors were rare and often overlooked or uncredited. The patent, preserved and digitized by institutional archives such as the University of Central Florida's library, ensures that Forbes's specific technical contribution remains part of the documented historical record of women's innovation in engineering and applied science.