Daniel Burgess, 38, of Cornwall, pleaded guilty to manslaughter after blocking the inflow and outflow pipes of neighbour Michael Hornder's house on Christmas Day 2015. He also glued a door lock.
Mr Hornder, 48, died of carbon monoxide poisoning.
Burgess was jailed for two years eight months at Exeter Crown Court on Monday.
The court heard Burgess, of Chywoone Avenue, Newlyn, used a large raw potato to shut off the pipe through which exhaust gases should have been vented.
He was taking revenge because he believed Mr Horner had stolen his pre-paid gas cards, with the result he could not heat his home.
His plan was to make Mr Horner suffer in the same way by sabotaging his heating, but a fault in the boiler meant an automatic fail safe system did not work and the house filled with gas.
Judge Geoffrey Mercer QC told Burgess: "You accept your unlawful and dangerous act in interfering with the flue of Mr Horner's boiler in the way you did caused his death.
"He had serious health issues and you knew of his disability and vulnerability."
A man has admitted killing his neighbour by putting a potato into the gas flue of his house.