Consumer NZ chief executive Sue Chetwin said the average savings at Pak'n Save on the basket of 40 grocery items was about $14.
Items in the basket included staples such as sugar, milk, butter and flour. Shoppers were instructed to buy the cheapest brand and a particular pack size.
Similar items were substituted if shoppers were unable to find a specified item. Fresh meat, fish and produce, as well as beer and wine were excluded because the survey method did not compare quality of items.
The battle for second place was less clear-cut, with baskets from Countdown and New World in different centres costing similar amounts.
But New World, which was most expensive in last year's survey, was cheaper in Christchurch and Dunedin.
Consumer found Countdown had the most products on "special" - nearly half the items bought in some stores were discounted.
But the watchdog noted that the regular price of at least some of these products was dearer than at other supermarkets, making savings look more attractive.
An addition to this year's survey was a price comparison of eight "top shelf" products from Countdown and New World, as well as Nosh in Auckland and Moore Wilson's in Wellington.
Pak'n Save was not included because it did not stock all the products, which included espresso coffee, organic milk, multi-grain bread, premium yoghurt and New Zealand olive oil.
Ms Chetwin said New World was the cheapest on price in every centre, beating Countdown by between $4 and $8. Both supermarkets were cheaper than Nosh.
