Aldi crowned the UK's cheapest supermarket in September

Aldi was the cheapest supermarket in September, according to the latest Which? analysis, once again pipping Lidl to the post.

In our analysis of 93 everyday grocery prices, Aldi cost £159.48 on average – £2 less than Lidl with Lidl Plus (£161.48) and £2.36 cheaper than Lidl without its loyalty scheme (£161.84).

Elsewhere, the loyalty price battle between Tesco and Sainsbury's raged on. Tesco came out on top this month with Clubcard beating Nectar after falling behind for the past few months.

Read on to find out how other supermarkets, including Asda and Morrisons, compare – and how much you could save by switching supermarkets.

Cheapest supermarket in September

We checked the prices of 93 popular branded and own-brand groceries, including milk, cheese and Hovis sliced bread, 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 supermarket once again, with a cost of £159.48 on average for the items on our list in September. 

Lidl, with its Lidl Plus loyalty scheme, came next with an average price of £161.48 – a difference of £2 compared to Aldi. Without its loyalty scheme, the average Lidl shop sat at £161.84. 

Asda was fourth cheapest, with our list costing £186.71 on average across the month. 

Tesco with Clubcard (£187.71) beat Sainsbury's with Nectar in September  (£188.95) – with a difference of just £1.24 between them. Morrisons with its More card followed, with an average shop costing £192.93. 

Without a loyalty card, the prices jump at Morrisons, Tesco and Sainsbury's. It was 20p more at Morrisons, £5.74 at Tesco, and £6.06 more at Sainsbury's for non-members in our analysis.

There were 46 loyalty discounts overall in September – 22 at Tesco, 21 at Sainsbury’s, two at Lidl, and one at Morrisons.

Waitrose was again the most expensive supermarket in our analysis, with the items coming to £223.38, followed by Ocado, where our list cost £208.64.

• Find out more: cheapest supermarkets of 2026.

How much of a discount do loyalty cards give?

A loyalty card would save an average of 0.1% at Morrisons and 0.22% at Lidl in September, according to our analysis. Shoppers save a little bit more at Tesco and Sainsbury's at 2.97% and 3.11%, respectively. 

Back in May, Lidl announced a big change to its loyalty card scheme. Now customers collect points rather than reward coupons; £1 spent equals one point. This brings the scheme into line with both Nectar and Clubcard.

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 aren't eligible to join the supermarket schemes due to their age, lack of address or difficulties with digital access. 

Earlier this year, Tesco announced a new Clubcard for 16 and 17-year-olds. The move comes after a major Which? campaign urging supermarkets to lift unfair restrictions on their loyalty schemes so more people can take advantage of lower prices. 

Although this is a win for consumers, more work is needed as certain restrictions continue to lock people out of valuable savings. Groups often affected include under-18s and those without smartphones, who may struggle – or simply not know how – to access loyalty prices.

• Find out more: loyalty schemes compared.

What has happened to the longer list?

We no longer publish research on the longer list of groceries as part of our monthly cheapest supermarket analysis, which included more branded items as well as own-brand items.

Instead, each month we publish our research on the cheapest supermarket for branded groceries separately, which we think will be of more use to shoppers as it will allow us to make more granular price comparisons. 

This new monthly tracker won't include Aldi and Lidl, as they don’t stock the same range of branded goods as the non-discounter supermarkets.

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

What's happening to grocery prices?

The UK inflation rate rose to 3.1% in the year to August, according to the Office for National Statistics (ONS). 

Grocery inflation also increased from 2.1% to 2.3% in the four weeks until 6 September, according to Worldpanel by Numerator. This rise comes after a period when grocery inflation was easing to its lowest since October 2024 in August. 

UK food inflation has not reached the levels forecast earlier in the year, amid fierce supermarket competition. However, the Food and Drink Federation industry body warned that food price inflation is likely to climb to nearly 4% by the end of the year and exceed 6% by the middle of 2027 due to the ongoing impact of the US/Iran war as well as extreme weather.

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

What are supermarkets doing to lower costs?

In September, Waitrose announced a £20m investment to lower prices across its stores. On average, Waitrose shoppers would see price cuts of around 11% on average across more than 370 of its grocery items. Some items, including porridge oats, bread, orange juice, and potatoes, saw price cuts of up to 20%. 

Back in August, Morrisons announced its new 'Unbeatable Prices' promise. The supermarket pledged to match or beat prices at Aldi, Asda, Lidl, Sainsbury's and Tesco across 500 core grocery lines including fruit and vegetables, bakery goods, cupboard staples and its Market Street counters. This replaces its previous 'Price Match' scheme, which saw it match prices with Aldi and Lidl across 200 core grocery lines. 

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 calculate the average price of each item across the month, then add those up to get each supermarket'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 like 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, to avoid supermarkets attempting to skew the results. 

We don't want supermarkets to compete with one another to lower prices only on the items they know they'll 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 can only include 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're 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.