[1] The Mountain Street substation is an unusual tuck pointed face brick structure on a corner site, designed in the Federation Free Style evidenced by the use of a sandstone window headers, sill detailing and gabled parapet with curvilinear elements and contrasting manganese banded brick parapet.

Stylistic elements also include a large arched entrance flanked by a ventilator and a multi paned window in the gabled wall and a pitched roof with exposed rafters.

The Mountain Street substation is constructed using load bearing face brick and sandstone block for the parapet.

[1] The Ultimo Substation was listed on the New South Wales State Heritage Register on 2 April 1999.

[1] This Wikipedia article was originally based on Substation, entry number 934 in the New South Wales State Heritage Register published by the State of New South Wales (Department of Planning and Environment) 2018 under CC-BY 4.0 licence, accessed on 13 October 2018.