Christmas is fast approaching and this week thoughts are already turning to what to cook and when, and for how long. And for many households it’s not just about getting everything done in time, but also making sure your bills don’t go through the roof as you jam all your appliances on for the next few days cooking for the whole family.

Money Saving Expert Martin Lewis has previously outlined how people should use their oven to cook Christmas dinner, not an air fryer. 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 traditional oven.

But Martin Lewis has tried to outline that it’s not always better to use an air fryer or a microwave over a traditional oven. Back in November 2023, Martin Lewis spoke on ITV’s This Morning where he stepped in after hearing a caller say they were going to cook their Christmas dinner in an air fryer.

Martin told the hosts of ITV’s This Morning: “I heard you on the show mention somebody is going to cook a Christmas dinner in an air fryer, is that right?

“If that’s been done for energy reasons I would be somewhat skeptical whether that is a good idea. If it’s been done for taste, I don’t wanna get involved.

“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 because air fryers are all the rage. They’re great for cooking small amounts. Be careful on it.”

Speaking later on his The Martin Lewis Podcast, available on BBC Sounds, Spotify and Apple Music, the finance expert set out exactly how and when you should and shouldn’t use an air fryer when cooking the Christmas dinner using his ‘rule of thumb’.

Martin Lewis 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 Kw per hour. 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.

“A microwave is also 1000W so per minute it’s the same cost as an oven, but things done in the microwave when you’re cooking a one-off, a one off jacket potato for example, is far more efficient because it’s 10 minutes in the microwave, it might be an hour and a half in the oven.

“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. That may well be effective if you’re cooking lots of stuff.

“But if you’ve got something small and simple in there, it’s probably cheaper and that’s where the microwave and also the air fryers tend to come into their own because they’re better at cooking single objects.”

He also talked about a method to cook a turkey that was outlined by a caller, called ‘spatchcocking’, otherwise known as ‘butterfly’. This is when you break the bird’s bones and spread it out instead of cooking it whole.

By doing so, you can reduce the amount of time the chicken takes to cook, thereby saving more money on running your oven (or air fryer!).