The Money Saving Expert Martin Lewis has delivered a stern warning to people swapping their ovens for air fryers.

The beloved expert has been inundated with questions from fans who are ditching their ovens for Ninja and Tower air fryers.

These devices are often promoted as cheaper alternatives to standard ovens, even leading some adventurous souls to contemplate roasting their Sunday dinners in them. But Martin voiced his doubts about such eco-friendly claims during his stint on ITV’s This Morning.

The questioning began as he probed: “I heard you on the show mentioning someone was gonna cook dinner in an air fryer. Is that right? If that’s being done for energy reasons, I would be somewhat sceptical whether that is a good idea.”

Lewis then elaborated further stating: “If it’s being done for taste, I don’t want to get involved. I mean, the benefit of an oven is when you’re cooking a lot for a lot of people, and you can fill all the racks and have it on consistently.

“Air fryers are good for small things that cook quickly. If you’re gonna have to use your air fryer 15 different times for different items generally on energy usage, you’d be better off to use an oven. So it’s an interesting thought.”

In a discussion about the cost implications of meal preparation, Martin scrutinised: “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.”

He proposed a straightforward equation for customers to contemplate, which involves determining the wattage of a device, then deducing “work out how many kilowatts or what fraction of a kilowatt it’s using, then multiply that by 34p per hour of use.”

According to Martin, this identical theory should be applied when evaluating the cost-effectiveness of air fryers and halogen cookers. He elaborated: “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.”

For those already orchestrating substantial meals, energy expert Llewellyn Kinch from MakeMyHouseGreen.com offered some guidance, advising: “If you cook a turkey in the oven for several hours, it’ll use up lots of electricity.”

“The savvy way is to use a slow cooker, which costs a fraction to run compared to a traditional oven. Crispy skin lovers can always finish the turkey in the oven for a short period of time.”

“For side dishes, opt for energy-efficient cooking methods, such as the microwave or convection oven. Roast potatoes come out well in energy-efficient air fryers. A final tip is to always match saucepan sizes to hot plates or burners, and keep lids on pots to reduce cooking time and energy waste.”