Buy non-sale goods at the wrong time of year and you could pay double
Consumer group Which? found some retailers charged more than double for products depending on when they were bought.
A Vax Blade 32v vacuum cleaner at AO.com, for example, jumped by 54%, costing £299 at its highest point but coming down to £139 at its cheapest.
There was also a Samsung fridge-freezer at John Lewis, which varied in price from £374.99 to £659. And a Brother printer on Amazon cost £114 at its cheapest and £199.98 at its most expensive.
Over a year-long period, the consumer group tracked the prices of 32 of the most popular makes and models of home and tech appliances across five of the biggest retailers: Amazon, AO.com, Argos, Currys PC World and John Lewis.
It said random pricing policy made it much harder for consumers to plan when to buy the products.
Some products maintained a steady price such as the Apple AirPod headphones, which were consistently £159 at all the retailers except for a short period around Black Friday where they dropped in price before returning soon afterwards.
Amazon offered the lowest prices more often than the other retailers in the investigation, while Currys PC World had the highest number of most expensive prices.
Alex Neill of Which? said: “Whilst we expect price variation across the year, our research shows that shoppers are often faced with wildly fluctuating prices and not necessarily during traditional sales periods.
“This can make it difficult for people to assess when a bargain is really a bargain, so we advise taking retailer hype with a pinch of salt, not feeling pressured by time-limited sales and doing your research before buying.”