The 33kV substation was built in 1938 for the Dunedin City Council Electricity Department to service the surrounding industrial area.
It became obsolete when it was recently replaced with modern, larger-capacity equipment.
DCC-owned Aurora Energy Ltd decided to preserve the building after discovering the cost of preservation was about the same as that of demolition.
''It is exceptionally attractive for a substation,'' Aurora chief executive Grady Cameron said.
''A series of interpretative panels have been produced and installed inside the building to describe the history and workings. The building remains within a live, high-voltage site and, unfortunately, it cannot be opened to the public. However, its preservation will leave a well-documented legacy.''
An office was once manned full-time and a part-time gardener employed on the site.
A wooden strip down the side of the office window supported a blackout curtain during World War 2, when bombing of vital utility assets was feared.
Windows facing the street were covered with mesh to prevent sabotage and a bomb-proof canopy was installed over the high-voltage transformers inside.
