We compared the prices of 63 popular grocery items and found that Aldi was the cheapest supermarket, closely followed by Lidl, even when loyalty prices at rival supermarkets were taken into account.
Shopping at Asda was also cheaper than shopping at Tesco with a Clubcard or Sainsbury's with a Nectar card for our list of groceries.
Read on to find out how your supermarket compares in the analysis.
Aldi prices beat Tesco Clubcard
Every day in July, we checked the prices of 63 popular groceries, including Heinz baked beans, milk and cheese, at eight of the UK's biggest supermarkets to see how they compared.
The chart below shows how much our shopping cost on average:
Waitrose was the priciest supermarket again this month, averaging £146.98 - £33.11 (29%) more than Aldi.
What about a bigger shopping list?
When we looked at a much larger selection (169 items), including more branded groceries, the savings offered by the loyalty schemes were bigger. Asda, which doesn't offer loyalty prices, was still cheaper, though.
Tesco offered Clubcard prices on 71 of the items at some point in the month but came second.
Sainsbury's Nectar - which offered loyalty prices on 93 of the items in our sample - was third.
These results show just how much more you'll pay if you stock up on a mix of own-brand and branded items at Tesco or Sainsbury's without a loyalty card.
For shoppers without a Nectar card, Sainsbury's was second-most expensive after Waitrose, while for non-Clubcard members, Tesco was just behind. Both were more expensive than Ocado.
Find out more:What level of discount do loyalty cards give?
Based on our smaller list of products, having a Clubcard would save you 2.1% at Tesco. At Sainsbury's, you would save 3.4% with a Nectar card.
For our longer list, which included more branded groceries and a bigger selection of loyalty discounts, the savings were much more substantial - 6.7% at Tesco and 7.1% at Sainsbury's.
But you would save even more money by switching to a discount supermarket.
Find out more:Why and how is Which? now including loyalty prices in the monthly comparison?
Which? started regularly including loyalty prices for the first time last month. We regularly review the way we analyse and report on prices as we want to give shoppers the most up-to-date and relevant information.
We can only take into account loyalty prices that apply to all members of a scheme (rather than those personalised to selected members), where there's one price on the shelf for shoppers with a loyalty card and another for those without. At the moment, this type of two-tier pricing is being used at Lidl, Morrisons, Sainsbury's, Tesco and Waitrose.
We can’t factor in points, personalised discounts or other rewards as these vary from customer to customer and don't always have a quantifiable monetary value that we could take off the basket totals we report on.
The Competition and Markets Authority is currently investigating grocery loyalty pricing and is due to report its findings in the autumn.
Some shoppers choose not to join loyalty schemes because they don't want to hand over their data, which retailers often sell to other companies and advertisers.
Our research last summer also found that many loyalty schemes have age and address-based restrictions, meaning some shoppers - including vulnerable groups - are unable to join and pay the lower prices on offer to members.
Find out more:What's happening to grocery prices?
Grocery prices were 1.6% higher in the four weeks to 7 July 2024 compared to the year before, according to market analyst Kantar. That's the lowest level of inflation since September 2021.
Football fans drove up purchases of beer, crisps and snacks on matchdays. But unseasonably wet weather boosted sales of fake tan and cold and flu treatments - and dampened demand for sun cream.
Prices are rising fastest for items such as vitamins, minerals, supplements, chilled fruit juices and drinks, and deodorants. They are falling fastest for toilet tissues, butter and dog food.
Find out more:source https://www.which.co.uk/news/article/which-was-the-cheapest-supermarket-in-july-aBKhB1L7prWC