The average power bill has increased by more than $100 over the past year.
Figures released by the Ministry of Business, Innovation, and Employment show consumers are paying an extra $117 on average for their electricity.
More than half of that increase ($67) is driven by a rise in transmission and lines costs, which is being passed on to the consumer.
The most expensive is in Northland, where lines company Top Energy has added $257 to bills in the past year.
Top Energy's chief executive Russell Shaw says that high cost is due to the company purchasing the transmission network previously owned by Transpower in Northland.
Mr Shaw says uneconomic lines throughout Northland, and one of the lowest customer densities in the country, also contributed.
Mr Shaw says lines charges are unlikely to increase in Northland over the next two years.