Consumers in the Hawke's Bay are being advised to shop around as power prices in some areas jump more than $200 from those a year ago.
Nationally, household power bills have risen by up to $358 in the year to August, and lines companies and retailers are blaming each other for the increases.
Figures from the Ministry of Business, Innovation and Employment (MBIE) show Hawke's Bay lines providers Unison, Centralines and Scanpower raised their lines charges by $39, $23 and $102 respectively in the past year (based on an average customer using 8000kW/h per annum).
Individual power companies responded by either not raising prices (Nova Energy) or lifting them by $254 (Genesis Energy).
A Genesis Energy spokeswoman said prices had risen due to an increase in rates in the Hawke's Bay during the past year.
"However this was the first increase since June 2010.
"Based on internal and external reviews of pricing, we believe we are still offering highly competitive rates in the Hawke's Bay," she said.
New Zealand's two million power consumers faced an average 5.4 per cent increase in their bills in the last year, the MBIE figures show.
Electricity Authority chief executive Carl Hansen said the Government's What's My Number campaign was launched to promote greater competition in the retail electricity market.
"Barring a major gas find or technology breakthrough, retail electricity prices are likely to continue to rise as demand increases over the next few decades," Mr Hansen said. "That is simply the reality of a natural resource-based industry, where generators tap the cheapest resources first and then the next cheapest and so on over time.
"However, promoting competition can and has made a difference."
From June to August, the What's My Number website saw 885,659 visitors, resulting in 490,117 households switching power companies.
An Electricity Authority report showed 881 households in the Hawke's Bay region left their power company in August.
Also, an international survey this month found New Zealand had the second-highest rate of consumers switching power companies, saving almost $9 million collectively.
VaasaETT, an energy think-tank in Finland, found that almost a fifth, or 19.5 per cent, of New Zealand consumers switched power companies last year, up from 10.5 per cent in 2008.
Increased competition and consumer switching has been credited with electricity prices dropping in 2011, Mr Hansen said.
However, power prices have since increased stemming from line charges increases.
Nationally, the biggest average increase for the year to August was Pulse Energy's $358 for its Nelson consumers using Marlborough lines.
At the other end of the scale, bills for TrustPower customers on Network Waitaki lines in Otago fell by $201.
NZ Federation of Family Budgeting Services chief executive Raewyn Fox said rising electricity costs were making it harder for poor families to get by.
The lower a family's income, the higher their power usage tended to be, Ms Fox said.
"One thing we do find is that the lower-income families for whom things are really, really tight tend to have older power appliances that are less power efficient ... they have really old heaters that chew through the electricity.
"They also tend to have lower quality houses that aren't as well insulated that have draughts around the windows and cheap curtains."
It becomes a downwards spiral, she said.
Rising expense
Hawke's Bay lines providers Unison, Centralines and Scanpower raised their lines charges by $39, $23 and $102 respectively in the past year to August.
Individual power companies responded by raising their prices by between $0 (Nova Energy) and $254 (Genesis Energy).
A total of 881 households in the Hawke's Bay region left their power company in August.
Based on an average customer using 8000kWh per annum.
Source: MBIE