The Act of Legislation incorporating the Grand Manan Light and Power Company was passed in 1928. By 26 June 1929, the company was organized at Grand Manan Island, New Brunswick. Owners of the company at the time of incorporation were: merchants Fred S. McLaughlin, Lawton C. Guptill, and A. LeRoy Ingalls; Dr. John F. McCulley, M.D.; merchant and fish exporter Joseph E. Gaskill; fish merchant John R. Moses; and others.

The diesel plant at Grand Harbour began operation in December 1929. The plant's capacity, however, proved insufficient. In 1938, electricity on the Island was turned off at 11 pm every night. The inhabitants of Grand Manan petitioned the New Brunswick Power Commission for electric light 24 hours a day. The commission responded by buying out the company. Louise Glennie, formerly secretary treasurer and manager of the company in the 1930s, became secretary to A. A. Dysart, one-time Chairman of the Power Commission and Premier of New Brunswick from 1935-1940.

The plant was expanded and staff increased several times. A second plant was built at Ingalls Head during the 1960s with a much increased capacity for production. Still, demand by industrial, commercial and home consumers strained this plant beyond its capacity. In 1970, a sub-marine cable was laid connecting Grand Manan with mainland supplies of electricity. The diesel plant is still operational and is turned on when there are emergency power outages on the mainland.