Bosco Connect, a subsidiary of Mercury Energy which often serves as the default provider in apartments, was singled out for bad customer experience.
"Thirty per cent of customers with Bosco had regularly experienced long wait times to speak to a customer service representative. It's overall rate of very satisfied customers was just 28 per cent," Chetwin said.
Chetwin said Bosco's price was a third more than the national average and apartment dwellers were often given the impression they have no other options.
"We're aware of one letting agent that wrongly told clients they had no choice of energy retailer," she said.
Flick Electric scored the top marks in Consumer NZ's survey with 71 per cent of customers saying they were very satisfied with the company's service.
Flick's prices are directly tied to the wholesale price of power. A recent surge in spot prices occurred due to low lake levels in the South Island.