Which was the cheapest supermarket in September?

Aldi has retained the title of cheapest supermarket for the second month in a row. 

We compared the prices of 71 popular grocery items and found Aldi beat Lidl by just £1.18 on average. 

None of the products on our list were included in Lidl Plus offers this month. 

Read on to find out where it was priciest to shop, plus how the supermarkets compared on a much bigger list of 186 products. 

Aldi the cheapest of the month

We checked the prices of 71 popular branded and own-brand groceries, including Hovis sliced bread, milk and cheese, at eight of the UK's biggest supermarkets throughout September, to see how they compared.

The table shows how much our shopping cost on average:

Aldi was the cheapest overall for our shop, beating rival discounter Lidl by a little over a pound. 

The next cheapest was Tesco if shopping with a Clubcard, where it cost 10% more on average for our shopping list. This was followed by Asda, which doesn't offer loyalty prices in the same way as the others. 

Shopping at Sainsbury's with a Nectar card was more expensive this month than shopping at Asda or Tesco without one, and 13% more expensive than Aldi across the month. 

Sainsbury's was running Nectar price promotions on 14 items on our list, and Tesco had Clubcard prices on 10. Meanwhile, Morrisons had one More scheme discount on items in our basket. None of the products on our list were included in Lidl Plus offers this month. 

Waitrose also offers some loyalty prices to members, but there were none for items on our shopping list this month. It was the priciest supermarket again this month, averaging £167.19 – that's £44.42 (36%) more than Aldi.

• Find out more: the cheapest supermarkets of 2025

What about a bigger shopping list? 

When we looked at a much larger selection (186 items), including more branded groceries, supermarkets' loyalty schemes made a bigger difference. 

Asda came out cheapest for this longer list, for the ninth month in a row, beating Tesco with a Clubcard by £6.79.

Tesco with a Clubcard – which had loyalty prices on 75 of the items – was the second cheapest, followed by Sainsbury's with Nectar and Morrisons with More.

Waitrose was most expensive again, at £531.39 – 14% more than Asda. 

Aldi and Lidl couldn’t be included in this comparison as they don’t stock all the branded products on the list.

You'll pay a lot more if you stock up at Morrisons, Sainsbury's or Tesco without a loyalty card.

For shoppers without a Nectar card, Sainsbury's was the second most expensive after Waitrose. 

• Interested in more than just price? Shoppers have rated product quality, customer service, online deliveries and more to reveal the best and worst supermarkets.

How much of a discount do loyalty cards give?

Based on our smaller list of products, having a loyalty card would save an average of 0.04% at Morrisons, 2.23% at Tesco and 2.85% at Sainsbury's over the month.

For our longer list, which included more branded groceries and a wider selection of items with loyalty discounts, the savings were much more substantial – 0.77% at Morrisons, 7.78% at Tesco and 7.82% at Sainsbury's.

The discounts offered by loyalty cards may sound good, but that's only if you can access them. Our research has found that millions of people can't access loyalty promotions because they're not eligible to join supermarket member schemes due to their age, lack of address or difficulties with digital access. 

We think that some supermarkets could do more to ensure certain groups of shoppers, such as those without a smartphone or those who are under 18, can access – or know how they can access – loyalty prices.

• Find out more: loyalty schemes compared

What's happening to grocery prices?

Annual inflation for supermarket food and drink has risen again – to 5.4% in the three months to the end of August 2025, according to our supermarket inflation tracker. That's up from 4.6% in May and 4.1% in February. It's still significantly lower than its peak of 17% in the three months to the end of April 2023, however.

Prices are rising faster for items such as chocolate, butter and spreads, biscuits and fresh meat. 

• Find out more: check what's happening to prices by supermarket, category of food and ranges using the Which? food and drink inflation tracker

How Which? finds the cheapest supermarket

We check the prices of hundreds of grocery items at eight major supermarkets, 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 one's average total price. 

What items are on the list?

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 several factors, including quality and weight.

Which? never shares the full list of products used in its analysis, as we want to avoid any attempts by supermarkets to skew the results. 

We don't want supermarkets to compete with one another to lower prices just on the items they know they will be judged on. Instead, we want retailers to work to make groceries affordable across the depth and breadth of their available lines.

What about special offers and loyalty prices?

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, and we can’t factor in points or other rewards, as these vary between customers and don't always have a quantifiable monetary value.

• Find out more: how to spend less at the supermarket