They were hailed as the must-have energy saving hack for hard up families across the country.
And as the cost of living crisis deepened, struggling households have snapped up air fryers in their hundreds and thousands. But now money saving expert Martin Lewis has some concerning news - it may not always be cheaper to use one of the nifty devices - or even a microwave - than an oven.
The frugal guru's warning comes as many have invested in air fryers from leading brands such as Ninja and Tower - thinking they are more economical than using a traditional cooker.
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But Mr Lewis said people need to think carefully before they switch from oven to fryer, reports the Mirror - as they may actually end up forking out more in some circumstances.
Speaking on his podcast, he said in the end it comes down to an equation of what uses more energy and obviously with an oven you have the need to heat it up beforehand, reported the Manchester Evening News.
He said: "The problem with the equation for heating equipment is an oven is going to be about 2000W. A microwave I believe, from memory, a best guess explanation, a microwave gives you consistent heat whereas an oven is warming up to full temperature and then topping it up so it isn't running at full power the whole time."
He continued: "But if you're doing a jacket potato for 10 minutes it's going to be far cheaper [in the microwave] than doing a single jacket potato in an oven and keeping it on for an hour and a half.
"However if you were doing a full roast dinner and you were cooking many of them, that is where it's probably cheaper than putting five or six jacket potatoes in a microwave because each additional object you put in a microwave, you need to keep it on longer because a microwave just heats the individual object.
"General equation is, find the wattage of an item, then work out how many kilowatts or what fraction of a kilowatt it's using, then multiply that by 34p per hour of use."
The same advice can be applied to air fryers and halogen cookers.
Mr Lewis went on: "If you had a 1000W microwave and you put it on for 10 minutes, one KWH for a sixth of an hour, a sixth of 34p is about 6p, shall we say? So it's 6p turning the microwave on for that amount of time. So yes it's a very useful equation."
His guidance comes as separate research carried out by the consumer experts at Which? revealed the cheapest cooking appliance for popular meals. For the majority of foods that were tested, the air fryer was found to be the cheapest as well as the quickest option.
Emily Seymour, Which? Energy Editor, said: "There has been a surge of interest in air fryers and smaller cooking appliances in recent months, and our research shows that the hype could be justified in some cases, as we’ve found these products cost less to cook certain foods than conventional ovens."
And the energy expert agreed with Mr Lewis' point on larger meals, stating: "The cost savings will soon be lost if you have to cook more than one batch though, so it’s still better to use your oven if you’re cooking large quantities."
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