[2][3] Large-scale electricity production came to New Hampshire in 1882 when the New England Weston Electric Light Company of Boston built a generating station in Manchester, on the property of the Amoskeag Manufacturing Company.

PSNH records indicate that at least 39 small electric companies that were in business before 1900 were combined over the years.

PSNH was incorporated in 1926 as a consolidation of five existing independent electric companies in New Hampshire.

[4] Among the power plants that the company built are Schiller Generation Station, three coal-fired units in Portsmouth, New Hampshire, which when opened in 1950 was the country's first fully integrated binary cycle plant, and the Seabrook Station nuclear power plant in Seabrook, New Hampshire, which began operating in 1990.

Cost and deadline overruns in the construction of Seabrook Station caused PSNH to declare bankruptcy in 1998, the first investor-owned utility to go bankrupt since the Great Depression.