Contact Energy is putting the increase in customers' energy bills down to rising input costs across the board.
Gas and electricity bills are expected to go up by an average of 11 percent from next month, with Genesis also doing the same.
More than 200,000 Contact customers will be paying around eight percent more for their electricity bills.
Chief Executive Mike Fuge told Mike Hosking the increase covers both lines charges and wholesale energy prices.
He says the latter has gone up by 50 percent in three years, and are expected to peak in the middle of next year.
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