He graduated from Bergen Cathedral School in 1877, and took the candidate.jur.
Degree in 1881. In 1882 he was hired as a clerk for the district stipendiary magistrate in Hallingdal. Already the next year he returned to Bergen to work as a merchant. He was also the Chief Executive Officer of the bank Bergens Sparebank.
Kahrs was elected to the Norwegian Parliament in 1904, but only served one term.
He was a member of Bergen city council in 1893 to 1910, serving as mayor from 1899 to 1901, preceded by Christian Michelsen and followed by Johan Ludwig Mowinckel, both of whom served as Prime Minister of Norway. Kahrs was a member of the board of Den Nationale Scene from 1892 to 1909, and chaired the supervising committee of the Bergen Lincolnshire.