Average weekly sales in three stores in Yorkshire, Cheshire and Manchester rose by 7.5% in the first three months after conversion.
These improved returns were over and above the higher performance levels usually produced at newly-developed stores, United said. The Perfect Store layout initiative is a joint venture between United Co-operatives and Unilever UK, and involves consultation with shoppers.
"This is an ongoing analysis and the initial results are encouraging even though the sample and timescales are still small," said United Co-operatives marketing manager Susan Beetlestone.
"Fresh areas, in particular produce and meat, performed best."
Unilever UK category strategy manager Suzy Ford added: "Although these are only results from three out of the eight stores in the trial, they show a consistent performance."