We compared the prices of 62 popular grocery items and found the total cost averaged £111.66 at Aldi, while Lidl charged just 67p more.
The price difference was even smaller – only 41p – when Lidl's loyalty promotions were taken into account.
Tesco was the cheapest of the traditional supermarkets with an equivalent shop averaging around £10 more for Clubcard members. However, non-members would have paid around £13 more.
Read on to find out which was the most expensive supermarket and where was cheapest for a longer shopping list.
Discounters beat Clubcard and Nectar prices
Every day in October, we tracked the price of 62 branded and own-label groceries – including a Hovis loaf of bread, Birds Eye peas and pasta – at eight supermarkets to see how their prices compared.
The table below shows how much our basket of groceries cost on average. Lidl, Morrisons, Sainsbury's and Tesco offered loyalty prices on some products, so we've calculated the average price for both members and non-members of their loyalty schemes.
Sainsbury's offered member-only Nectar prices on 20 out of our 62 items. Tesco had Clubcard prices on 13 and Lidl and Morrisons both ran loyalty promotions on four items.
Find out more:Where was cheapest for a bigger shop?
We also compared the average cost of a longer shopping list of 164 food items (the original 62 plus 102 more) including more branded items. This analysis didn't include Aldi or Lidl as they stock a limited range of branded products.
Asda was the cheapest supermarket at £418.71. Members of its Rewards scheme also would have earned £2.99 cashback on products with loyalty promotions.
We haven't factored this into our main analysis because loyalty members don't receive a discount on the day and cashback is only redeemable at Asda, within a limited period (up to nine months) and in increments of £1.
Tesco was only 1% pricier than Asda when loyalty card promotions were taken into account (£422.54), but shoppers without a Clubcard would have paid 7% more (£449.99).
Morrisons was the third-cheapest supermarket (£428.32) if you have a More card, and cheaper than Tesco and Sainsbury's if you're not signed up to their loyalty schemes.
Waitrose was the most expensive supermarket again at £461.10. The total cost of our shop was also 10% more at Sainsbury's if you're not a Nectar member (£459.58).
Problems accessing loyalty promotions
New Which? research has found millions of people can't access loyalty promotions because they're not eligible to join the member schemes of supermarkets and health and beauty retailers. This includes teenagers, homeless people and those without online access.
We found you must be 18 or over to join loyalty schemes at Asda, Lidl, Sainsbury's, Tesco and Waitrose, or 16 at Morrisons. You can sign up at a younger age at Sainsbury's if you're added to the card of a parent or guardian.
Several loyalty schemes also restricted access to people without an email address, smartphone or a UK address or residency.
Find out more:How Which? compares supermarket prices
We check the prices of hundreds of grocery items at eight major supermarkets every day throughout the year, using an independent price comparison website. For each supermarket, we work out the average price of each item across the month, then add those up to get each store’s average price.
Our shopping list comprises the country’s most popular and widely available groceries, based on extensive market analysis. It includes branded items such as Cathedral City cheddar and Hellmann's mayonnaise, as well as own-brand products such as potatoes and baked beans.
Own-brand items won’t be identical across supermarkets, but we’ve ensured everything we’ve compared is as similar as possible based on a number of factors, including quality and weight. We include special offers but not multibuy discounts.
We are only able to take into account loyalty prices that apply to all members of a scheme (where there's one price on the shelf for shoppers with a loyalty card and another for those without). Currently, this type of two-tier pricing is used at Lidl, Morrisons, Sainsbury's, Tesco and Waitrose. We are unable to include discounts that are personalised to selected members.
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.
Find out more:What's happening to grocery prices?
Food inflation slowed to 1.9% in October, down from 2.3% in September, according to the British Retail Consortium (BRC).
Inflation slowed on meat, fish and tea products. Prices continued to rise faster for packaged food at 3.1%, while fresh food inflation fell to 1%.
The BRC said prices had also eased for chocolate and sweets as retailers tried to tempt customers with Halloween offers.
Find out more:source https://www.which.co.uk/news/article/cheapest-supermarket-in-october-acfNy7V4XpMs