He was flown to Hutt Hospital.
Featherston fire chief Colin McKenna said it appeared the man had possibly spilled liquid on himself while cooking at an electric oven, and the liquid may have caught fire.
Mr McKenna went to the house in Western Lake Rd, finding evidence of a fire which was extinguished.
"It's obvious he's spilled liquid on the floor."
Mr McKenna said police are involved.
A man and a woman, who accompanied the victim to the helicopter, would not comment to the Times-Age.
A road worker, who didn't want to be named, said the man was "shaking" as the staff soaked him down.
Gusto cafe manager Gina Richards said the man appeared in "terrible shock".
"He was badly burned, he couldn't say anything, he was so badly burned.
"We got buckets straightaway."
Featherston senior station officer Lee McKenna said the shop staff "did a fantastic job of minimising his injuries.
"We're very thankful to the help provided to him."
Life Flight crewman Logan Taylor said the man was "in a bit of pain" but in a stable condition during the flight.