In 1925, the English consultancy of Merz & McLellan was commissioned by then Minister of Railways, Gordon Coates, to report on electrifying the suburban networks in Auckland, Wellington, Christchurch and Dunedin. The report, released in August 1925, recommended that of the Christchurch system, only the Lyttelton line warranted electrification due to the volume of traffic and the Lyttelton tunnel. To operate the line, Merz & McLellan recommended purchasing five electric locomotives to haul all trains on this line, and that electric multiple units would not be necessary. The new electrification should be the same 1.5 kV DC as used at Otira and later in Wellington.