Sainsbury's shoppers with a Nectar card pay £849 more on average for their food shopping per year compared to those who shop at Aldi, according to new analysis from Which?. The consumer watchdog named the in May 2025, following analysis of 82 branded and own-label . A weekly shop for these items, which included essentials like bread, milk and cheese, came to £135.48 at Aldi in May, making it the cheapest out of eight assessed by Which?.

Fellow discounter Lidl was close behind at just 31p more for shoppers who have its Lidl Plus loyalty app, with a weekly shop costing £135.79 - or 34p more at £135.82 if you don't have the app.

Of the traditional supermarkets, Asda came out as the cheapest without any loyalty discounts with the 82 items costing £149.94, followed by Tesco with a Clubcard at a cost of £150.26.

But Sainsbury's shoppers pay more than this for the same list of items - even with a Nectar card. By comparison to Aldi, Sainsbury's shoppers with a Nectar card pay £16.34 more for the same grocery list, with the 82 items totalling £151.28.

Over the course of a year, the difference in cost compared to Aldi means that Sainsbury's Nectar card shoppers would pay a whopping £849.68 more for 52 weekly grocery shops than customers at Aldi, if prices remain at the same level.

Without a Nectar card, the 82 items totalled £155.59 - £3.77 more than those with a loyalty card pay, and £20.11 more than at Aldi.

Which? said: "Aldi was the cheapest supermarket in May, charging £135.48 on average for our shopping list of 82 branded and own-label groceries. Fellow discounter Lidl was hot on its heels, at just 31p more if you have its Lidl Plus loyalty app (£135.79), or 34p more if not (£135.82).

"Asda, which doesn't offer loyalty discounts in the same way, was the cheapest of the traditional supermarkets - our shopping cost £149.94. Waitrose was the most expensive supermarket at £184.03 - 36% more than Aldi."

As for larger shops, Which? also compared the average cost of a selection of 198 items - the original 82 plus 116 more - and found Asda to be the cheapest out of the traditional supermarkets once again, with the total cost averaging £485.79. Both Aldi and Lidl were excluded from this analysis as they don't stock many of the branded items.

Tesco with a Clubcard was the second cheapest at £496.59 (£10.80 more on average compared to Asda), while Sainsbury's with Nectar was the third cheapest at £498.72 (£12.93 more on average compared to Asda).

But Sainsbury's shoppers without a Nectar card pay significantly more on average, with the 198 items totalling £537.81 - £39.09 more than with a loyalty card.

Reena Sewraz, Which? Retail Editor, added: "Aldi continues to be the UK's cheapest supermarket in our monthly price analysis for May while Lidl has narrowed the gap to just 31p. For a bigger list of groceries, Asda continues to be the cheapest supermarket, beating shopping at Tesco with a Clubcard by more than £10.

"Food prices are still high and are likely to rise again so many people will be looking to cut costs where they can. Our analysis shows that by switching supermarkets, shoppers could pay up to 36% more, highlighting the advantages of shopping around where possible."