Lentz was born on 21 July 1859 in South Africa. When he was six years old, his father died and the family returned to relatives in Germany. He became an engineer in the Prussian Navy.
In 1888, Lentz founded his own machine factory in Vienna. At an exposition in honour of Alessandro Volta in Como in 1899, his first steam engine won the first prize. At the Exposition Universelle (1900) in Paris, it won the Grand Prix while Lentz himself was awarded the gold medal.