When the NZR decided to electrify the Lyttelton tunnel near Christchurch due to the known problems with the operation of steam locomotives, they ordered six locomotives from English Electric. They were delivered in 1928 and were similar to the EO built by the same company in 1922. But in comparison to these, they had a longer wheelbase, more power and a higher gear ratio for a top speed of 53 mph or 85 km/h. They were designated EC since they were used around Christchurch.
In this tunnel, they hauled freight trains of 600 tons and boat trains of 400 tons. When the first one was withdrawn in 1967 due to its age, diesel traction was introduced on this line. By September 1970, all had been withdrawn and replaced by diesel locomotives. Soon the overhead lines were removed altogether. EC 7 was the only one that has been preserved. Today it is being operated on the Ferrymead Railway, together with EO 3.