Martin Lewis explains when using air fryer is more expensive than an oven

Money expert Martin Lewis has a 'rule of thumb' to explain when using an air fryer is actually more expensive than a traditional oven.

The trendy kitchen appliance has become a bit of a sensation in recent years as people look to find cheaper ways of cooking their dinner than running a big gas or electric oven - and air fryers also have the advantage of healthier oil-free cooking as well as often being quicker to cook. But has tried to outline that it's not always better to use an or a microwave instead of a traditional big oven.

Speaking on his Martin Lewis Podcast on BBC Sounds, and Apple Music, the finance expert has previously set out exactly how and when you should and shouldn't use an when cooking the dinner using his 'rule of thumb'.

Energy supplier Utilita, in its Power Price List, set out that an air fryer costs £26.73 to run for a year for an average user, whereas a gas oven costs £33.22, and an electric oven £93.44, although these numbers are often subject to change depending on the latest Ofgem price cap changes, and will vary hugely depending on how long you use them for, and what tariff you're on.

But as Martin says, an oven has a much larger capacity, so if you're cooking multiple things at once for a long period, you could end up having a lower cost for that meal than if you'd used an air fryer. So an air fryer is only actually cheaper in practice if you don't need to fill your oven's capacity and you're cooking 'single objects'.

said: "Let me give you my simple rule of thumb.

"First of all, find the wattage of the appliance you're using. If you've got a heated gilet, it might be 50 watts. When I talk about 'heating the home' it is a lot cheaper to have a heated gilet or something that just heats you rather than heating the whole room.

"Then remember 1,000 watts is a kilowatt. And you pay roughly 34p per kilowatt per hour [now about 27p in the latest prices, but the rule is the same].

"So if you had a heated gilet on for an hour, it's around a 20th of 34p which is around 1.7p per hour.

"Now an oven is typically 1-2000w so you're paying around 34p or 68p an hour.

"An oven isn't always using all the wattage as it's heating up and then topping up.

"So if you've got a turkey in there that may well be effective if you're cooking lots of stuff in there and it's on for a couple of hours.

"But if you've got something small and simple in there.... that's where the microwave and also the air fryers tend to come into their own because they're better at cooking single objects."

Martin added that smaller appliances like air fryers and microwaves are not going to be cheaper for doing several items at once like an oven can. He said: "The problem with the equation for heating equipment is an oven is going to be about 2000W.

"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.

"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."