Powershop's price per unit of electricity was, however, still lower than Mercury's at the end of the survey period. "We had a [price] catch-up last April," said Powershop's chief executive, Ari Sargent.
"We were lagging behind on previous years on recovery of line costs and metering costs."
He said there had been a lot of "finger-pointing" in the industry over price rises, "with retailers blaming lines companies and Transpower and them fighting back. Retailers should take responsibility for their own prices, cut costs where they can and help customers to save power."
Mr Sargent said the national 2.9 per cent increase found by the survey was lower than the rises in the preceding two years, because of the declining contribution of big increases in electricity transmission prices.
"We expect price increases from now on to be much closer to inflation," he said.
His company's analysis also calculated how much money an average consumer could save in each region if they switched from the dearest to the cheapest retailer - more than $100 a year everywhere except Southland.
The East Coast's Wairoa area topped the list with potential savings of $656 a year; Tauranga came ninth on $538; and Aucklanders on the Vector network 24th on $363.
Mr Sargent urged people to shop around for the best deal, but also noted many were locked into fixed-price contracts carrying stiff break fees if they tried to switch retailer.
Domestic Energy Users' Network convener Molly Melhuish said: "Prices have always been higher in the regions. Competition has brought prices down significantly in the regions, but they are still higher than where competition is strong."