Following the success of the electrification of the Midland Line between Arthur's Pass and Otira, it was decided in 1925 to introduce electrification to Lyttelton. On 14 February 1929, the electrified line was opened using a 1.5 kV DC system, with an electrical substation at Woolston. This was originally intended to be the first stage of a larger plan for Christchurch passenger services. Six EC class electric locomotives operated passenger services between Christchurch and Lyttelton, until reaching the end of their working lives in 1970, with the last electric train service running on 19 September 1970. With the withdrawal from service of the EC locomotives, the electrification was removed as the cost of purchasing replacement locomotives and maintaining the electric infrastructure could not be justified. The Electric Traction Group based at the Ferrymead Historic Park has preserved and returned to operational status locomotive EC 7.