His best-known inventions are the U.S. electrical plug and the pull-chain light socket. In 1888, at the age of thirty-one, Hubbell quit his job as a manager of a manufacturing company and founded Hubbell Incorporated in Bridgeport, Connecticut, a company which is still in business today, still headquartered near Bridgeport. Hubbell began manufacturing consumer products and, by necessity, inventing manufacturing equipment for his factory.
Some of the equipment he designed included automatic tapping machines and progressive dies for blanking and stamping. One of his most important industrial inventions, still in use today, is the thread rolling machine. He quickly began selling his newly devised manufacturing equipment alongside his commercial products.
Hubbell received at least 45 patents. Most were for electric products. The pull-chain electrical light socket was patented in 1896, and his most famous invention, the U.S. electrical power plug, in 1904, this brought the convenience of portable electrical devices, already enjoyed in Great Britain since the early 1880s, to the U.S.