Harold had worked as a singer and actor before his marriage, most notably in Edmund Yates' production Invitations at the Egyptian Hall, London, 1862–63.

After a couple of years Power ran away from his farm work and joined a theatre stock company at St. Augustine, Florida, debuting as Gibson in Charles Hawtrey's The Private Secretary on 29 November 1886, aged 17.

Following this success, Power appeared in a few more original stage productions like Chu Chin Chow (American version) and The Wandering Jew.

After an extremely prosperous 30 years of acting on the stage and touring around the world, Power moved into silent films in 1914.

In 1916, Power played the male lead in Where Are My Children?, a serious film about birth control and social issues directed by pioneer director Lois Weber and her husband Phillips Smalley.

Also in 1921 Power appeared in D.W. Griffith's Dream Street in which experimental synchronised sound was used, using the Photokinema sound-on-disc system.

Power then prepared to film a sound remake of The Miracle Man, which had been a great silent success in 1919 for Lon Chaney.

While filming The Miracle Man, Power died of a heart attack on 23 December 1931 in the arms of his 17-year-old son at his apartment at the Hollywood Athletic Club.