Contact and Mercury customers in the Far North are paying 12 per cent more for power, and, with line charges included, an average of $560 more per annum.
The ministry's figures show big differences between power companies. In the Far North Genesis and TrustPower had not increased their prices in the year to May 15, leaving Contact Energy the most expensive (36.5c/kWh) and Genesis the cheapest (28.33c/kWh). In Whangarei Contact and Empower charge the most (29.6c/kWh) and Genesis the least (26.02c/kWh).
Northland's representative on the New Zealand Federation of Family Budgeting Services, Eliza Waenga (Kaitaia), said the power price hikes were bringing "terrible hardship" to a region that was already struggling with high unemployment.
She had spoken to a client on Tuesday who had to find an extra $30 a week on top of the $35 she had been used to paying for power.
"Our clients are on a tight budget anyway. They're having to use the little they put away for car registration and warrants of fitness to pay for power instead," Ms Waenga said.
"The next thing they'll have to use is food money, which won't help the health problems we have up here already."
Top Energy chief executive Russell Shaw said the increase in Far North line charges, the highest in the country, was the result of the company taking over assets from national grid operator Transpower, including the Kaikohe and Kaitaia substations and the high-voltage line between them. The good news for Far North consumers was that line charge increases would now be limited to single figures.
The only households to be hit with a bigger increase in power charges than Northland over the last year were Pulse Energy customers in Nelson/Marlborough, and the only people who are paying more for power than Contact Energy customers in the Far North are some Contact customers in Otago and Buller.
To check whether you are paying too much for power, find a recent power bill and go to www.whatsmynumber.org.nz or www.powerswitch.co.nz Once you type your power usage and location into the on-line calculator it will tell you how much other companies in your area will charge. A similar service, also free, is provided by www.switchme.co.nz If you don't have a computer the Citizens Advice Bureau can help. For more power-saving tips go to www.consumer.org.nz or www.energywise.govt.nz