The State controls the generation of electricity. The Water Power Act of 1903 reserved to the Crown, with certain exceptions, the sole rights to generate electricity by water power. Delegation of these rights was later permitted and the law was finally consolidated in the Public Works Act of 1928. The State Supply of Electrical Energy Act was passed in 1917 “to regulate the generation, sale, and supply of electrical energy by the State and to provide for a system of accounts …”. This is the statutory machinery which the State Hydro-electric Department, established by the Electricity Act of 1945, took over from the Hydro-electric Branch of the Public Works Department. The Electricity Amendment Act of 1958 created a separate portfolio of electricity and the name of the Department was changed to New Zealand Electricity Department.

In 1953 the Geothermal Energy Act gave the Crown the sole right to tap and use geothermal energy and also provided for licences to be issued for the private and commercial use of geothermal steam.