He was born in Storkow, Brandenburg and gained a doctorate in Administrative Law from The University of Göttingen in 1911.

From 1930 to 1934 he served under Carl Goerdeler as the deputy mayor and treasurer of the city of Leipzig.

He joined board of the Friedrich Krupp AG in 1934 as Director of Administration and Finance.

Löser was arrested in its aftermath and on 20 October 1944 was tried by the People's Court, but succeeded in convincing Roland Freisler that he was suffering from memory loss.

In 1947, Löser was indicted at the Krupp Trial for war crimes, including use of slave labor and plunder of occupied Europe.