Which? exposes supermarket pricing secrets that could lead to you paying over the odds for grocery products

Shoppers could be paying almost four times more than they need to for the same branded grocery products at certain times, Which?’s biggest ever supermarket pricing investigation has found.

The consumer champion analysed more than a million prices for 493 branded grocery items at six major supermarkets – Asda, Morrisons, Ocado, Sainsbury’s, Tesco and Waitrose – throughout 2020. 

The investigation revealed not just the pricing secrets that mean shoppers could be paying over the odds for the same products depending on the days they shop, but also the types of grocery products that fluctuate the most when it comes to price, as well as the supermarket that almost always beats its rivals when it comes to the cost of branded groceries 

Lavazza Qualita Rossa Ground Coffee (250g) at Ocado had the most dramatic price difference, as the investigation found shoppers could pay almost four times more for the same product on different days. It was at its cheapest price of £1.30 for 63 days in 2020, however for more than a third of the year (130 days), it cost an eye-watering £5 – a 284 per cent difference for the same product. Ocado said this price fluctuation was an error that has now been corrected.

The price for Müller yogurts illustrates the so-called “high-low” tactic used by many supermarkets – when prices are dramatically hiked and then slashed at regular intervals. For example, Müller Light Greek Luscious Lemon yogurts fluctuated substantially at Sainsbury’s during 2020, flipping between £1 and £2.75 – a 175 per cent price difference – at roughly three-week intervals. The same product was also available for £1 or less in at least one of the major supermarkets for about 85 per cent of the year.

Other products that saw significant price variations included Carte D’Or Vanilla Ice Cream and Loyd Grossman Tomato and Basil Sauce at Asda – with prices fluctuating by 133 per cent and 125 per cent respectively. 

At Morrisons, shoppers could pick up a bottle of Shloer’s Red Grape Juice Drink for just £1 on a good day, however it cost more than double (£2.25) on other days – representing a 125 per cent increase.

Which? also found there were price variations of 122 per cent for Jordans Country Crisp Four Nut Cereal at Tesco. Shoppers could sometimes pay just £1.35, yet on other days the same pack was more than double the price at £3. 

The investigation also analysed pricing at a category level, looking at 19 areas from chocolates to cheese, and found the price for branded cakes and biscuits fluctuated by 48 per cent on average – more than any other category.

In this category, Which? analysed the price of 14 products and found a 10-pack of Cadbury Chocolate Mini Rolls at Asda had the biggest price difference. It cost just £1.20 at its cheapest but was more than double the price at £2.60 on certain days. 

Shoppers should also keep a close eye on the price of juices and smoothies, as prices in this category varied by 41 per cent on average. This was followed by cooking sauces (38%), crisps (36%) and cereal (35%). 

Across all 19 categories analysed, Asda had the lowest average prices for branded groceries, making it the best option for shoppers who prefer branded items but do not want to pay over the odds. 

Waitrose was the most expensive supermarket for branded items in eight categories including energy drinks, ice cream and tea, and Ocado for seven categories including juice drinks, coffee and cheddar.

Almost all the products in the investigation varied in price and could be found discounted at one or more supermarkets at any time. However, a Which? survey found one in five shoppers are confused by grocery promotions and the majority (73%) would prefer consistently low prices. 

While Aldi and Lidl were not featured in the investigation as they stock fewer branded goods, they have won legions of customers by focusing on consistently low prices rather than deals and discounts. In Which?’s monthly price analysis, the cheapest supermarket is invariably either Aldi or Lidl.

Ele Clark, Which? Retail Editor, said: 

“Our research reveals just how wildly food and drink prices can fluctuate from day to day, meaning people are at risk of massively overpaying for branded groceries depending on when and where they shop. 

“We would recommend keeping an eye on the prices of your favourite products and stocking up when they’re discounted to avoid paying over the odds.”

Notes to editor 

Which? analysed more than a million grocery prices for branded items at six major UK supermarkets: Asda, Morrisons, Ocado, Sainsbury’s, Tesco and Waitrose throughout 2020. Aldi and Lidl were not included in the investigation as the discounters stocked fewer branded items. 

In March 2021, Which? surveyed 2,000 adults in the UK. Fieldwork was carried out online by Opinium and data has been weighted to be representative of the UK population (aged 18+). 


Please see a link below for the average price fluctuation for all 19 categories: 




  • Don’t pay full price – If you regularly buy non-perishable branded groceries such as crisps, cereal and tins of soup, make sure you stock up when they’re discounted and avoid paying full price for them. 
  • Shop around – Although they don’t offer online grocery shopping, Aldi, Lidl, Home Bargains, Wilko and others often offer good deals on branded products too. It’s also worth trying own-label alternatives, which can offer great quality at even better prices.
  • Watch out for pricing tricks – Discounts are great but don’t be manipulated by other pricing tricks. The strawberries may be on offer but what about the price of the upmarket pouring cream temptingly positioned next to it?
  • Scrutinise price-matching claims – Sainsbury’s and Tesco both shout about their Aldi price-matching schemes, but they actually only cover a limited range of products, so the total cost of your shopping may still be higher than it would be at Aldi. 
  • Take advantage of supermarket loyalty scheme discounts – Lidl Plus and Tesco Clubcard are just two examples of supermarket loyalty schemes offering exclusive discounts to members.


Which? awards various endorsements to supermarkets: 

  • Lidl was awarded Cheapest Supermarket of 2020 – link here
  • Waitrose won the Which? Award for Supermarket of the Year in 2020 – link here.
  • Aldi was named the UK’s favourite in-store supermarket for 2021 in Which?’s annual satisfaction survey – link here
  • Sainsbury’s was the highest-scoring online supermarket of 2021 in Which?’s annual satisfaction survey and was also named a Which? Recommended Provider for its online services – link here.
  • Aldi was awarded the Cheapest Supermarket for April – link here.


Right of reply

An Asda spokesperson said: ‘’We have a long heritage in providing customers with the brands they love at the best possible prices and we’re really pleased the Which? survey found that Asda is the cheapest supermarket for branded products. Investing in price to provide even greater value for customers when they shop remains our key strategic priority. In tandem with everyday low prices, we are also focussed on a number of other price investments to deliver great value, including our regular rollbacks and price lock events, where prices are reduced across thousands of food and non-food categories.”

A Sainsbury’s spokesperson said: “We’re committed to offering our customers the best possible quality and value and prices fluctuate up and down for a variety of reasons. Our Price Lock and Sainsbury’s Quality Aldi Price Match campaigns ensure customers can feel confident they are getting the best possible prices at Sainsbury’s, while not compromising on quality.”

An Ocado spokesperson said: “Ocado is committed to offering customers the best range, service and value in the market. As part of this commitment, we are proud to offer over 49,000 products – more than any other supermarket. Our Value Delivered range offers hundreds of everyday items at low prices. The fluctuation in price for the Lavazza product was due to a technical error and has since been resolved. The regular price is now back in place and is in line with most other major grocery retailers.” 

Morrisons, Tesco and Waitrose did not provide a comment. 

About us

Which? is the UK’s consumer champion, here to make life simpler, fairer and safer for everyone. Our research gets to the heart of consumer issues, our advice is impartial, and our rigorous product tests lead to expert recommendations. We’re the independent consumer voice that influences politicians and lawmakers, investigates, holds businesses to account and makes change happen. As an organisation we’re not for profit and all for making consumers more powerful.

The information in this press release is for editorial use by journalists and media outlets only. Any business seeking to reproduce information in this release should contact the Which? Endorsement Scheme team at endorsementscheme@which.co.uk.

Press Release: , , , ,