Powell was prosecuted after evidence of the crime turned up during a police investigation into the disappearance of his daughter-in-law, Susan Powell. He was convicted May 16.
His defense team argued for a lighter sentence while prosecutors urged Pierce County Superior Court Judge Ronald Culpepper to impose a 10-year sentence, The (Tacoma) News Tribune reported.
Detectives searching Steven Powell's files in August 2011 for information on his daughter-in-law found a computer disc, "disc 12," with images of a neighbor's two young daughters taken surreptitiously while they were undressing or using the bathroom in their home outside Puyallup, Wash.
The two girls and their mother testified during the trial. The mother said Powell filmed her daughters -- who were 9 and 8 at the time -- in various stages of undress, and that she'd learned about it from an investigator.
"He explained to us that when we lived at our rental house, our neighbor had taken pictures of us," the mother said.
Investigators have said they are convinced Susan is dead and named her husband as a person of interest, although he was never charged. Josh Powell killed himself and his sons in February in an explosion at his rented home in Puyallup.