[3] He was engaged in England to Eva Beatrice Ellis, whom he married at St Alban's Church, Armadale in Melbourne on 11 January 1902 and had four children.
On return to England he supervised a number of tramway and town lighting systems.
In 1889, he was sent to Melbourne as assistant to F. W. Clements, to manage the Brush Electrical Engineering Co subsidiary Electric Light and Traction Co. Harper became electrical engineer to the Melbourne City Council in 1901 (replacing Arthur Arnot), where he was involved in the expansion of the generation and distribution system including introducing three-phase transmission and a new generator at Spencer Street Power Station.
He recommended the establishment of a public utility on the lines of the Ontario Hydro Electricity and was appointed to the government brown coal advisory committee (chaired by Department of Mines director Hyman Herman).
This led to him becoming the first chief engineer on the State Electricity Commission of Victoria retiring in 1936.