Martin Lewis air fryer warning: Why your kitchen gadget might be costing you more

You've probably heard the hype. Everyone and their grandmother seems to have a Ninja or a Tower air fryer sitting on their kitchen counter these days. They’re fast, they make chips taste incredible without the vat of oil, and the marketing tells us they’re basically money-printing machines for our energy bills. But hold on a second. Martin Lewis, the man behind MoneySavingExpert, has been waving a bit of a red flag lately. He isn't saying throw your air fryer in the bin. Not at all. He's just saying we might be using them all wrong if the goal is purely to save cash.

It’s easy to get swept up.

Honestly, the Martin Lewis air fryer warning boils down to a simple math problem that most of us ignore because we’re too hungry to care. We see a gadget that uses 1,500W and think it must be cheaper than a 2,200W oven. And usually, for a handful of nuggets or a single jacket potato, it is. But there is a "tipping point" where the efficiency falls off a cliff.

The big "tipping point" for your energy bills

The core of the issue is capacity. If you’re cooking for one or two people, the air fryer is almost certainly the winner. It heats up in about two minutes. An oven? That’s fifteen minutes of "dead time" where you're just paying to heat up a big box of air.

But here is where the Martin Lewis air fryer warning gets real. If you are trying to cook a full Sunday roast for a family of five, and you find yourself running the air fryer in three separate batches because the basket is too small, you’ve messed up. You are now running a high-wattage device for three times longer than necessary.

Why the oven wins for big meals

• Thermal mass: Once an oven is hot, it stays hot. It’s insulated. It "tops up" the heat rather than running at full blast the whole time.
• Space efficiency: You can shove three trays of food in an oven at once. An air fryer usually has one or two small drawers.
• Batch cooking: Running three 20-minute air fryer cycles (60 minutes total) often uses more electricity than one 40-minute oven cycle.

Martin Lewis explained this clearly on his podcast and during appearances on ITV's This Morning. He notes that while a microwave or air fryer is great for "single objects," the energy cost scales up with every extra item you add. In an oven, adding a second tray of potatoes doesn't double your energy bill. In an air fryer, if you have to cook them separately because you can't overlap them without getting "soggy bottom" syndrome, you are literally doubling your cost.

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Doing the math: The Martin Lewis "Rule of Thumb"

If you want to be a nerd about it (and let's be real, that's why we listen to Martin), he gave us a formula. It’s not as scary as it sounds. Basically, you find the wattage of your machine.

Let's say your air fryer is 1,500W. That is 1.5 kilowatts (kW).
If energy costs roughly 34p per kWh (the unit price varies, but this is a solid benchmark), then running that air fryer for one hour costs:
$$1.5 \text{ kW} \times 34\text{p} = 51\text{p}$$

Now, compare that to your oven. A typical electric oven might be 2,000W ($2 \text{ kW}$).
$$2 \text{ kW} \times 34\text{p} = 68\text{p per hour}$$

On paper, the air fryer is cheaper per hour. But if the air fryer takes 20 minutes ($17\text{p}$) and the oven takes 40 minutes plus 15 minutes of preheating ($62\text{p}$), the air fryer is a massive win. However, if you have to run that air fryer four times to feed the whole family? Suddenly you’re at $68\text{p}$, and you’ve spent over an hour swapping baskets while half the food gets cold.

It's not just about the electricity

There's a hidden side to the Martin Lewis air fryer warning that people often forget: the "food waste" and "quality" factor. Consumer group Which? has backed up Lewis’s skepticism. They found that for large quantities, the oven is simply more practical.

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Then there's the bacon issue. Dietitians have actually chimed in here too. Brenda Peralta once pointed out that cooking super fatty foods like bacon in an air fryer can cause the fat to drip onto the heating element, causing smoke, odors, and potentially a messy cleanup that requires even more hot water (and energy) to scrub away.

When to definitely use the oven

1. Roast Dinners: Too many components. Don't try to fit a turkey, parsnips, and sprouts in a Ninja. It won't end well.
2. Batch Baking: If you’re making 24 cupcakes, use the oven racks.
3. Complex Meals: Anything requiring more than two different "zones" of temperature or timing.

When the air fryer is king

• Reheating Pizza: Seriously, it’s better than the day it was delivered.
• Frozen Snacks: Chips, nuggets, fish fingers. Done in half the time.
• Single Proteins: One salmon fillet or a couple of chicken thighs.

The gas oven plot twist

Here is something that really throws a wrench in the works. Gas is significantly cheaper per unit than electricity. If you have a gas oven, the "cost per hour" is often way lower than a 1,500W electric air fryer.

According to The Eco Experts, a gas oven can cost as little as 23p per hour to run. Even if it takes longer to cook the food, the raw cost of the fuel is so much lower that the air fryer might actually be the "luxury" option. Most people assume "new tech = cheaper," but when it comes to gas vs. electric, the old-school blue flame often wins on the balance sheet.

Practical steps for your kitchen

So, what do you actually do with this information? You don't need to do a calculus equation every time you want a snack. Just keep these three "MSE-style" rules in mind:

First, think about the volume. Is the food going to be crowded? If you have to stack things in layers, they won't cook right anyway. Air fryers need air to circulate. If you're stuffing it full, it’ll take longer, and you'll lose that "fried" crunch. Use the oven for big piles.

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Second, check your fuel. If you’re on a prepay electric meter and have a gas stove, use the gas. It’s almost always going to be the better financial move for anything that takes longer than 15 minutes.

Third, use the "Spatchcock" trick. If you must use the air fryer for a whole chicken (which Martin mentions can be done), butterfly that bird. Flattening it out increases the surface area and cuts the cooking time by a massive margin. Less time "on" means more money in your pocket.

The bottom line? The Martin Lewis air fryer warning isn't an attack on the gadget. It’s a reality check. Don't let the "efficiency" marketing trick you into running a small machine for four hours when the big machine could have done it in one.

Actionable Next Steps:

1. Check your manual: Look up the exact wattage of your air fryer. It’s usually on a sticker on the bottom or back.
2. Compare to your oven: If you have an electric oven, it’s likely 2.0kW to 2.5kW.
3. The 30-minute rule: Generally, if a meal takes more than two "batches" in the air fryer, or if the total cooking time exceeds 40 minutes, switch to the oven.
4. Audit your gas: If you have a gas oven, try to use it for "long-haul" cooking like casseroles or roasts; the unit price of gas is roughly 1/3 to 1/4 the price of electricity.