Which’s monthly analysis involves comparing the average prices of a shop consisting of popular groceries at eight of the UK’s biggest supermarkets.
The cheapest supermarket for a shopping list of 63 items was Aldi, where the groceries cost £113.87 on average across the month.
Fellow discounter Lidl was just behind Aldi in July, costing £2.37 more (£116.24 on average).
Waitrose was the most expensive supermarket this month, totalling £146.98 – a difference of £33.11 compared to Aldi – 29 per cent more.
The list of 63 items included a number of both branded and own-brand items, such as Heinz baked beans, Hovis bread, milk and butter.
The analysis includes special offer prices and loyalty prices where applicable, but not multi buys.
Tesco Clubcard members would have paid £127.50 – while without a Clubcard, the Tesco shop cost £130.27.
For those using a Sainsbury’s Nectar card, July’s shopping list of items cost £129.81, which is £15.94 more than at Aldi and still higher than the prices at Lidl (£116.24) and Asda (£125.61). Without a Nectar card, the same items at Sainsbury’s cost £134.41.
While Lidl, Morrisons and Waitrose do also operate two-tier pricing, their schemes are currently on a smaller scale and this month, no items on Which?’s list were available at a lower price to members of these schemes.
This latest pricing analysis from Which? demonstrates that shoppers can make considerable savings on their groceries depending on where they buy their food.
Ele Clark, Which? Retail Editor, said:
“Our latest monthly analysis has once again seen Aldi retaining its crown as the UK’s cheapest supermarket.
“With the ongoing pressure of high food prices on household budgets, it’s no surprise that many people are turning to the discounters to save money. Consumers could save over £30 simply by switching supermarkets, which goes to show how beneficial it can be to shop around.”
