Shoppers are often faced with “wildly” fluctuating prices on the most popular home and technology appliances, making it difficult to determine genuine bargains, a consumer group has warned.

Which? tracked the prices of 32 of the most popular makes and models of appliances over a year across Amazon, AO.com, Argos, Currys PC World and John Lewis, finding “considerable” variations in almost all cases.

The watchdog acknowledged that consumers could expect price reductions during sale periods, including the Black Friday event, but found several examples of fluctuations at other times, including a Vax vacuum cleaner at AO.com that varied from £299 at its highest point to £139, a 54% price difference.

An LG television at Currys PC World varied in price by 48% from £328 at its cheapest to a maximum of £629 across the year, while a Samsung fridge-freezer at John Lewis and a Brother printer at Amazon both varied in price by 43%.

Which? said the retailers’ pricing policies made it difficult for consumers to plan when to buy products.

AO.com, Currys PC World and John Lewis all offer price-matching schemes for customers, although these all have slightly different rules about what is included.

Alex Neill, Which? managing director of home products and services, 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.”

John Lewis said: “We’re not surprised by these findings as our commitment to our Never Knowingly Undersold policy means that when our competitors run promotions we lower our prices to match.”

An AO.com spokeswoman said: “Our customers expect value for money so we constantly review and match prices which, coupled with our exceptional service, is why millions of people chose AO.com for buying electricals.”