Cheapest supermarket in September: can Clubcard and Nectar prices beat the discounters?

Aldi was the cheapest supermarket in September, even when loyalty promotions at bigger supermarkets were taken into account.

We compared how much supermarkets charged for a selection of 59 groceries last month and found the total cost was £102.68 at Aldi – around 10% less than at Tesco and Sainsbury's, even when Clubcard and Nectar offers were included. An equivalent shop at rival discounter Lidl cost £1.18 more than at Aldi. 

Asda was also cheaper than Tesco or Sainsbury's, despite not offering member-only discounts.

Waitrose was the most expensive supermarket, with an average price of £130.37 – 27% more than Aldi. But when we compared the cost of a bigger shopping list, Sainsbury's was the priciest supermarket for shoppers without a Nectar card.

Read on to find out how much our shopping list cost Clubcard and Nectar members versus non-members.

Asda beats loyalty prices

We checked the price of 59 food items, including semi-skimmed milk, pasta and Cathedral City cheddar, at eight supermarkets every day in September to see how they compared.

The table below shows the average cost of our basket of branded and own-label groceries.

Aldi was the cheapest overall at £102.68 on average, with Lidl charging just £1.18 more.

Asda was the cheapest of the traditional supermarkets at £112.19, but it only just beat Tesco and Sainsbury's when their loyalty prices are taken into account: Tesco shoppers with a Clubcard would have paid 77p more, while Sainsbury's shoppers with a Nectar card would have paid £1.60 more.

Sainsbury's had member-only Nectar prices on 19 of our 59 items, while Tesco offered Clubcard prices on five. Shoppers without a loyalty card would have paid 5% more at Sainsbury's and 0.4% more at Tesco on average.

Lidl, Morrisons and Waitrose also offer member-only discounts, but they didn't run any loyalty promotions on the groceries on our shopping list in September.

• Find out more: best and worst supermarkets for in-store and online shopping

Where was cheapest for a longer shopping list?

We also compared the total cost of a bigger list of 164 food items (the original 59 plus 105 more) including more branded products. This analysis didn't include Aldi or Lidl as they only stock a limited range of branded goods.

Asda was the cheapest supermarket at £418.88, but it only beat Tesco – where the average cost for Clubcard members was £418.89 – by a penny. However, non-members would have paid 8% more at Tesco, at £452.92.

Sainsbury's was the third-cheapest supermarket (£421.16) for Nectar cardholders, but the most expensive supermarket if you're not a member (£461.29) – that's 10% pricier than Asda and costlier even than upmarket Waitrose.

However, a recent Which? investigation found loyalty prices aren't always good as they appear. 

When we checked, 10% of Tesco's loyalty offers had been at the non-member price for less than half the previous six months, which calls into question whether non-member prices can be considered a fair reflection of the 'usual' selling price. 

The prices in question were also on average 10% higher than Waitrose's, which is surprising given Waitrose is regularly the priciest in our monthly supermarket comparison.

Some 5% of Sainsbury's loyalty promotions had non-member prices that had been in place less than half the time, and these were 13% higher than Waitrose's.

• Find out more: Which? investigation finds loyalty prices aren't always good as they appear

How Which? compares supermarket prices

We track 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 we 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 a Hovis loaf and Birds Eye peas, as well as own-brand products such as grapes and carrots. 

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). At the minute, 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: how to spend less at the supermarket

What's happening to grocery prices?

Food inflation increased slightly to 2.3% in September, up from 2% in August, according to the British Retail Consortium (BRC). Prices rose faster for packaged food at 3.3%, while fresh food inflation increased to 1.5%. The BRC said poor harvests across the globe had driven up the cost of cooking oils and sugary items.

Last month, the Which? supermarket inflation tracker revealed chocolate had the fastest-rising prices of the 20 food and drink categories we track – 11% in the month to the end of August 2024 – followed by vegetables (5%). Butter and spreads, milk and cheese are all now cheaper than a year ago.

We also found budget-range own-label food and drink had a higher rate of inflation than standard or premium own-label and branded ranges.

• Find out more: Which? food and drink inflation tracker