Southern Electricity Supply was a corporation sole that controlled and administered the electricity supply assets of the New South Wales Department of Public Works, from 1942 to 1950. It operated a number of coal-fired and hydro-electric power stations in New South Wales, and was a bulk electricity supplier to part of New South Wales, mainly in the south and south central-west of the state. In November 1950, its assets and operations were merged into the Electricity Commission of New South Wales.

The Electricity Commission of New South Wales, sometimes called Elcom, was a statutory authority responsible for electricity generation and its bulk transmission throughout New South Wales, Australia. The commission was established on 22 May 1950 by the Electricity Commission Act 1950 to take control of power generation in the State. The commission acquired the power stations and main transmission lines of the four major supply authorities: Southern Electricity Supply, Sydney County Council, the Department of Railways and the Electric Light and Power Supply Corporation Ltd, also known as the Balmain Electric Light Company, the owner and operator of Balmain Power Station. The commission was responsible for the centralised co-ordination of electricity generation and transmission in the State, and some local councils continued to be distributors of electricity only.