The 89-year-old widower, who wishes to remain anonymous, lives alone in a five-bedroom house on the Taieri.
He said he usually paid less than $200 a month for power.
He believed the "mighty big jump" was due to running his heat pump all day every day because of the recent colder weather.
He set the heat pump, which was installed about eight years ago, to about 25degC during the day and dropped it to 17degC at night.
Only the lounge area, which had ceiling insulation, was heated, meaning the rest of the house was "very cold".
To reduce his power bill, he had started using a wood burner again and would remove one freezer and one hot water cylinder from his home.
Although able to "cope" with the bill, he paid it "reluctantly" because he believed power "should be for the people" and not cost so much.
He was concerned for others who were struggling to pay for heating costs this winter.
"How can the average man, on the average wage, paying rent for a house, how can he live?"
