Kevin Manley, 39, received £3,750 after a judge ruled jail operators G4S had taken too long to fix things.
Manley tripped over a slipper in the dark and banged his head on a cupboard.
Judge Neil Bidder told Cardiff County Court electricity should have been restored to cells at Parc Prison in Bridgend, Glamorgan within 20 minutes.
One victim was stabbed in the arm with a cheese knife and the other chased and hit over the head with a metal bar.
The decision to award Manley damages for his power cut fall was greeted with outrage by ex-Home Office minister Ann Widdecombe.
She said: “The judge needs his head examining.”
A G4S spokesman said: “We are going to be considering what further legal action is available to us.”
Manley, who has since been released, declined to comment.