The four largest retailers are losing market share, with medium-sized retailers gaining 40,000 new customers last year, according to the Electricity Authority's annual review.
Although large retailers have so far lost only a small percentage of their market share, the competition from mid-sized retailers, and the entry of eight new independent retailers in the last 18 months, is putting downward pressure on prices.
Over 20 percent of consumers switched suppliers last year, which the authority said is the highest rate in the world.
But chair of the authority, Brent Layton, said it was curious that only a third of consumers were interested in shopping around for the best deal, even though it is easy to do so.
He said the authority would like to see consumers becoming more proactive when it comes to choosing a retailer and it was working on ways of making it easier to do that.
Meanwhile, the What's My Number? website can help consumers compare retailers.