Sebastian Ziani Pietro Innocenzo Adhemar de Ferranti, designer, inventor and electrical engineer, was born in Liverpool in 1864. His parents were Cesar Ziani de Ferranti (1831–1903), photographer, and his wife, Juliana, a talented concert pianist. Cesar Ziani de Ferranti ran a successful portrait photography business, and Sebastian grew up in a comfortable household. He attended St Stanislaw Prepatory School in Hampstead, London. He showed talent as an artist, but was already beginning to experiment with steam engines. In 1877 his family sent him to St Augustine's, Ramsgate, Kent, a Benedictine boarding-school, where the staff encouraged his experiments and introduced him to science of electric lighting. In September 1880 he matriculated at University College, London, to continue his studies. Unfortunately his father's untimely death threw Ferranti's family into financial difficulties, and he had to abandon his degree.

de Ferranti began his working career at Siemens, working alongside inventor Alexander Siemens, designing alternator armatures. At Siemens firm he met the photographer Alfred Thompson. Thompson and Ferranti managed to capture the interest of solicitor Francis Ince in their business ideas. As a result the electrical engineering firm of Ferranti, Thompson, and Ince Ltd was established by September 1882. The firm collapsed within a year, and was swiftly followed by another short-lived venture, before Ferranti achieved success.

From 1885 Ferranti established his global reputation as a leading advocate of high-tension alternating-current (AC) generation and distribution. Through work conducted on behalf of Sir Coutts Lindsay & Co, Ferranti demonstrated the feasibility of his ideas, and would become involved in establishing the London Electricity Supply Corporation (LESCo.). Ferranti was a pioneer, as he set up the world's largest power generators at Deptford Power Station. From Deptford the distribution pressure of 10,000 volts would be sent along cables and transformers, a world first.

LESCo struggling financially, and ended the relationship with Ferranti in 1891 but Ferranti's unique expertise had already led to his establishing S. Z. de Ferranti Ltd, a private limited liability company formed in 1890. From the mid-1890s onwards demand for electricity took off, and by 1896 Ferranti decided to rent larger premises in Hollinwood, near Oldham, Lancashire. The company would remain there for the next seventy years.

Two businesses were established at Hollinwood in the early years: one successfully producing meters, and one for steam alternators, which ran into difficulties. This led to Ferranti being largely excluded from the business for over a decade. During this time he worked on other projects, including working with J. and P. Coats Ltd on textile machinery, with Vickers on resuperheating turbines, and with J. Hopkinson & Co. on steam stop valves. He also worked as a consultant for the new, large-scale electricity supply companies.

Ferranti had married Gertrude Ince, daughter of his former business partner, and had seven children. By 1913 his wealth allowed him to buy Baslow Hall, near Bakewell in Derbyshire. He played an active role in industrial politics and professional engineering circles, for instance taking on the presidency of the Institute of Electrical Engineers in 1911-1912. The University of Manchester awarded him an honorary doctorate in 1912.

During the First World War, Ferranti Ltd became heavily involved in munitions work. It would also play a role in the development of Britain's National Grid, and diversify into electrical products for domestic consumers.

Sebastian de Ferranti died 13 January 1930 at the Kantonsspital, Zürich, Switzerland, following surgery. By the time of his death he had one hundred and seventy-six patents under his name, and had played an influential role in the development of electricity. His eldest surviving son, Sir Vincent Sebastian de Ferranti (1893–1980) took over his father's role at Ferranti Ltd.