"Retailers then determined how and when they passed these costs on to their customers."
Powerco's distribution charges made up on average 35 per cent of the overall costs electricity retailers passed on to customers, Mr Warren said.
Nationally, household power bills have risen by up to $358 in the year to August.
MBIE figures show New Zealand's two million power consumers faced an average 5.4 per cent increase in their bills in the last year.
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.
"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."
There were 885,659 visitors to the What's My Number website from June to August, resulting in 490,117 households switching power companies.
New Zealand Federation of Family Budgeting Services chief executive Raewyn Fox said rising electricity costs were making it harder for poor families to get by or put food on the table.
"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."
The lower a family's income, the higher their power usage tended to be, Ms Fox said.
"They can't afford to fix the seals around their fridge and stove and they have really old heaters that chew through the electricity."
Rising costs
Wairarapa lines provider Powerco increased its lines charges by $82 in the year to August. In response, power retailers raised their prices by:
Genesis Energy: $115
Contact Energy: $96
Empower: $96
Energy Direct NZ: $71
Energy Online: $189
Just Energy: $170
Mercury Energy: $137
Meridian Energy: $76
Powershop: $134
Pulse Energy: $194
Tiny Mighty Power: $122
TrustPower: $0
Nova Energy: $112
(Based on an average customer using 8000kWh per annum)
- Source: MBIE
