Power prices have almost doubled over the past decade.
Figures issued by the Domestic Electricity Users Network show power prices increased by 87% between 2000 - 2011.
Previous figures showed prices rose by almost 69% between 2000 - 2009.
The network says the rate of increase has slowed since 2009, but the rise is still hefty.
Spokesperson Molly Melhuish says power companies are constraining prices because of low wholesale rates, flat demand and political pressure to keep prices down in an election year.
But she expects power companies will move next year to lift prices, particularly for residential customers.
The Electricity Authority says it plans to introduce more measures to increase competition.
But chief executive Carl Hansen says that won't necessarily result in lower electricity prices.
