Victorian Supreme Court Justice Andrew Tinney described Stuart Lee's crimes as "shocking and heartless" as he handed down sentence on Thursday.
"The pain and anguish you caused... is incalculable," the judge said.
Lee pleaded guilty to murdering Colin Bainbridge at a Wheatsheaf property in regional Victoria on March 14, 2023.
Mr Bainbridge had been felling trees in his friend's backyard when, without any instigation, Lee yelled at him to "f*** off".
Mr Bainbridge said the same thing in response and Lee rushed off to call the police.
After five calls went unanswered, he finally told an officer he would go and murder his neighbours if they did not come.
The 65-year-old then went into his shed, poured petrol from a jerry can into a blue bucket and grabbed a lighter from inside the house.
Lee went into the backyard, climbed a fence and poured the petrol over Mr Bainbridge before setting him on fire.
Mr Bainbridge's son Joshua, who was working nearby, rushed over and helped put out the flames with a hose.
He was airlifted to The Alfred hospital with burns to 81 per cent of his body and died later that evening.
In sentencing Lee on Thursday, Justice Tinney accepted the 65-year-old had a personality disorder which made him inexplicably suspicious of his neighbours.
But he rejected arguments from defence that Lee was genuinely frightened of Mr Bainbridge, instead finding he acted only in anger.
"Your indignant anger overcame your clear understanding of the wrongfulness of your actions and you committed murder," Justice Tinney said.
Lee will be eligible for parole after 27 years.
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