UK shoppers are finding it difficult to work out the best value items amid confusing supermarket practices, consumer group Which? has warned.
Some versions of the same product can cost up to three and a half times (346%) more per unit at the same supermarket, Which? found.
In one example, up to 17 different-sized versions of Coca-Cola (KO) were available with prices varying between 11p and 50p per 100ml at Tesco. That’s 346% more for a shopper who buys four 250ml glass bottles for £5 than one who picks up a 1.5 litre bottle for £1.68 instead.
The research also found that the price per 100ml of own-brand semi skimmed milk varied between 6p and 13p at Morrisons — that’s 133% more for a shopper choosing a 500ml bottle at 65p rather than choosing a 2.27-litre bottle for £1.27.
As part of the investigation, Which? tracked the prices of 10 popular groceries including Cadbury's Dairy Milk chocolate, Nescafe instant coffee and Weetabix at the "Big Four" supermarkets — Asda, Morrisons, Sainsbury's (SBRY.L) and Tesco (TSCO.L) — for three months.
"At a time when food prices are a huge concern, unit pricing can be a useful tool for shoppers to compare and choose the cheapest groceries but unclear supermarket pricing means the vast majority of people are left struggling to find the best deal,” Sue Davies, Which? head of food policy, said.
“Small savings can add up and make a big difference but unless supermarkets make unit pricing much more prominent, legible and consistent — as well as displaying it on their promotional offers — people will continue to risk missing out on getting the best value,” she added.
Which? also found fruit and vegetables such as pears and tomatoes which, depending on the pack size or variety, were given a price each, per pack, or per kilo — making it "difficult" to compare prices.
There were also issues with terminology across different supermarkets, such as for peppers at Lidl, which were priced both per "piece" and "each". Meanwhile at M&S (MKS.L), "each" was used to mean both a pack of four pears and also a single pear.
When Which? looked at major supermarket websites — Amazon Fresh (AMZN), Asda, Iceland, Morrisons, Ocado (OCDO.L), Sainsbury’s, Tesco and Waitrose — it found all displayed unit pricing for standard-priced items and for discounted items. But researchers were unable to find unit pricing for multibuys at any of the supermarkets, although not all the discounters offer this.
At Tesco, the supermarket with the biggest market share, Which? found most discounts are now offered through Clubcard Prices, which don’t show unit pricing. That means most discounts in Tesco are difficult to compare with other similar products.
The displaying of prices of goods and therefore unit prices is governed by the Price Marking Order 2004 but the legislation specifies a range of different units that can be used depending on the product type, which result in confusion for shoppers.
A Lidl spokesperson said: “We always endeavour to ensure that pricing information is as clear as possible for our customers so that they can make informed purchasing decisions.”
A Waitrose spokesperson said: “We regularly review all our products to ensure our unit pricing is clear and consistent, so that customers can compare prices and save money. Our partners are always on hand to assist customers with any pricing queries.”
All other supermarkets that were part of the research did not comment.
Which? is calling on supermarkets to make unit pricing “more prominent, legible and consistent” — as well as by displaying it on their promotional offers.