Choosing the right supermarket can significantly impact your grocery bill, but a new investigation by Which? reveals that timing is equally crucial. The consumer group tracked prices of thousands of popular groceries from March 2025 to March 2026 at Asda, Morrisons, Ocado, Sainsbury's, Tesco, and Waitrose, uncovering clear patterns of rotating three-to-four-week discount cycles.
Key Findings
Several grocery staples, including Kellogg's Special K cereal, Tropicana Orange Juice, and Fox's Chocolate Biscuits, were on offer at one major supermarket or another every single day of the year. Which? experts described this as 'alarming', noting that the sheer frequency of promotions makes the listed 'full price' misleading.
Examples of Discounted Items
- Kellogg's Special K Original Cereal (440g): Full price £3.30-£3.50, but available for £2.85 or less somewhere every day. Ocado had it on promotion 51% of the time, Tesco 50%, Waitrose 48%, and Asda and Morrisons 29%.
- Tropicana Orange Juice Original (1.5L): Full price £4.28-£4.75, discounted to £3.50 or less 99% of the year.
- Fox's Chocolatey Milk Chocolate Biscuit Rounds (130g): Full price £2-£2.75, on offer for £1.75 or less 99% of the year.
- Nestlé Shredded Wheat Cereal (625g): Discounted to £3 or less 97% of the time.
- Onken Set Natural Yogurt (450g): Regularly marked down throughout the year.
- Kettle Chips Lightly Salted Crisps (130g): On promotion every day at one retailer.
Extreme Price Swings
The investigation also found extreme price fluctuations. For example, a four-pack of Light & Free Peach Passion Fruit Greek Style Yogurt varied by 190%, costing £1 at Ocado and £2.90 at Waitrose. Asda had the largest single-store hike on Amaara plain poppadoms (200g), which rose from 48p to £1.50.
Advice for Consumers
Which? offers several tips to maximize savings:
- Decode Shelf Labels: Supermarkets hide promotion end dates in different ways. Tesco reverses the end date, Sainsbury's shows the start date, and Waitrose uses a four-digit code.
- Shop Different Aisles: Check world food aisles for cheaper bulk grains and spices, or the baking aisle for larger packs of dried fruit and nuts.
- Audit Unit Pricing: Always judge value by price per 100g or 100ml, not the flashy banner.
- Avoid Convenience Outlets: Smaller stores can charge up to 21% more than larger supermarkets.
- Utilise Price Trackers: Asda remains the cheapest baseline for branded items, while Sainsbury's and Tesco (without loyalty cards) are most expensive.
Reena Sewraz, Which? retail editor, said: 'Supermarkets are using dizzying pricing cycles to create a false sense of urgency, but our investigation blows the lid off these endless promotions. When items like Tropicana and Special K are on sale nearly every single day of the year, the “full price” becomes entirely meaningless.' She advises shoppers to ignore flashy promotions and focus on unit pricing to see what they are actually paying.
