(hydroelectricity generated 84.5% of New Zealand's electricity in 1980), and therefore electric trains do not have to rely on imported oil to operate. Classification Initially, the locomotives were classified as "EAC" in planning documents. During the contracting process, some memorandum referred to the locomotives as E30. When the class began entering service, they were classified as "Class 30." In 1989, this changed again to EF. Service Introduction The electrification of the central section began in 1984, with the government setting aside NZ$40 million to purchase a fleet of locomotives to operate the new electrified line. Specifications for the locomotives were released in 1983. The contract to build 22 electric locomotives was awarded to Brush Traction of Loughborough, England in 1984. The first two, numbered 30007 and 30013, arrived in 1986 and were used in the testing of the new electrification system, while the remaining 20 locomotives were introduced after the electrification of the NIMT was completed. The locomotives are able to generate a continuous power output of , making the class the most powerful to operate on the New Zealand railway network. They also feature the unusual wheel arrangement of Bo-Bo-Bo, which had been previously used on the EW class electric locomotives and the DJ class diesel-electric locomotives. The advantage of using the Bo-Bo-Bo arrangement over the traditional Co-Co arrangement is that it provides greater flexibility for New Zealand's lightly laid and sharply curved tracks, resulting in less wear on the rails. The locomotives are supplied electricity from overhead lines. These lines draw electricity from New Zealand's national grid at four locations along the electrified section: Bunnythorpe, Tangiwai, Taumarunui, and Hamilton. The locomotives are fitted with regenerative braking as well as regular air brakes, so the traction motors can be turned into generators when the locomotive is coasting downhill and feed electricity back into the overhead lines and the national grid. The EF class were nicknamed "Toasters" or "Shoe Boxes" by New Zealand rail enthusiasts due to their boxy shape. In service The EF class were first used to haul freight trains along the central section of the NIMT, with the completion of electrification in 1988. Freight trains travelling from Auckland would be diesel-hauled to Te Rapa, change there to an EF locomotive and be hauled to Palmerston North where they would be changed back to a diesel locomotive to continue to Wellington. This remains the practice today, although trains