Hawke's Bay-based lines company Unison says increased electricity distribution charges will be repeated next year.
Unison customer care and relationship manager Danny Gough said the increase was the equivalent of an extra $10 per month for the average consumer, but electricity retailers may not immediately pass on the increase.
"If the retailers choose to pass these costs through, we believe an average household using 8000 kWh a year will get an increase of about $10 per month," Mr Gough said.
The increase, effective from April this year, incorporates higher Transpower (national grid) charges.
Next year's rise was expected to be at a similar level, Mr Gough said.
The most common residential lines tariff will increase 12.4 per cent. The most common non-residential lines charge will increase 10.8 per cent.
Mr Gough said the Commerce Commission identified 16 distribution companies (including Unison) that could raise their prices to ensure integrity of service.
"Because we are a monopoly, the Commerce Commission dictate to us what we can and can't do in terms of pricing.
"They have given us permission to put our prices up to a level that they believe is fair and reasonable, as long as we are ensuring we are operating a sustainable business in line with their objectives - to promote long-term benefits to the consumer.
"We realise that times are tough - we are in a soft economy and it will have an impact on our consumers.
"That is something we are very cognisant of, so we try to limit the increases as best we can.
"Ten dollars a month, for a lot of people in our community, is a hell of a lot of money."
Unison operates in Hawke's Bay, Taupo and Rotorua and is owned by electricity account holders in Napier and Hastings.