A very small oven with a very big opinion of itself

His grandson Tyler dumped a bag of frozen fries into a black plastic box the size of a bread maker, pushed two buttons and walked off to find a ketchup bottle. Grandpa watched him go. Then he pulled the drawer out, looked inside, slid it back, pulled it out again, and finally lowered himself onto one knee to inspect the underside of the machine.

"Where'd you hide the oil?"

"There's no oil, Grandpa."

"Then it isn't a fryer, son. It's a drawer with ambitions."

Seven minutes later the thing beeped and lit up with one word: SHAKE. Grandpa hasn't been ordered to shake anything since a dance hall in 1968. He took it personally. He shook the basket anyway, because he's a team player and because those fries were starting to smell very good.

What it says it does

An air fryer is a countertop convection oven. A heating element sits up top and a strong fan drives hot air around a small chamber. Because the chamber is small, it heats fast and browns the outside of food in a way that looks and crunches a lot like frying. A light coat of oil helps. A pot of it is never involved.

You'll see two main shapes. Basket models have a pull-out drawer with a perforated tray, and you shake the food halfway through so it browns evenly. Oven-style models have a door and racks, and some add rotisserie or dehydrating. Dual-basket versions cook two things at once at different settings. And plenty of countertop toaster ovens now include an air fry mode, which is the same idea with more room and a toast button.

Makers list capacity in quarts. Small baskets suit one or two people. Bigger ones and oven styles are aimed at families.

What Grandpa thinks it does

"It's a hair dryer for potatoes." He's said this at every family gathering since, and he's not entirely wrong.

He believes the name was invented by somebody in marketing, because nobody ever lined up around the block for a "small convection oven." He's also noticed it's the only appliance in history with its own cookbooks, its own paper liners, its own oil mister and its own fan club.

His favorite observation is that food from it gets announced at the table like a new baby. "These are air fried," somebody says, and everybody nods respectfully. In fifty years of marriage, he points out, nobody has ever said "these were ovened."

And he's done the real math. "It costs two square feet of counter. Paid monthly. Forever."

Where he has a point

It's small. Feeding five means batches, and the first batch is lukewarm by the time the last one comes out. Crowd the basket to save time and you get steamed, soggy food, which defeats the whole point.

It doesn't fry. Breaded food does well. Wet batter drips straight through the basket and bakes onto the bottom like a science fair volcano. Keep that one for a real fryer or skip it.

The basket is the weak spot. Most baskets have a nonstick coating, and metal tongs, steel wool and harsh scrubbers wear it down. Some baskets are dishwasher-safe and some aren't, so read the manual. Before you buy, check whether the maker sells replacement baskets and trays. If it doesn't, a scratched basket can mean a whole new machine. Your regular oven and a sheet pan have never needed that kind of babysitting.

It wants room to breathe. Hot air leaves through a vent, usually at the back. The manual tells you how much clearance to leave, so follow it, keep it off the stovetop and keep the vent clear of walls, curtains and paper towels.

Plug it straight into a wall outlet. Not an extension cord. Not a power strip. These machines pull a lot of power, and the wattage is printed on the label and in the manual. If running it alongside the microwave and the kettle trips your breaker, that's the circuit telling you something. Listen to it.

Never preheat with a loose paper liner inside. With no food holding it down, the fan can lift it into the heating element and set it on fire. Liners go in with the food on top, or not at all.

Some models want an app. Wi-Fi air fryers ask for an account and a phone to do what a dial already did. If you go that route, read smart home kit that earns its place, and kit that just sits there first, and give that account a strong, unique password like everything else in lock down every account you own in one evening.

Recalls happen. Air fryers have been recalled before. Search the model number on the Consumer Product Safety Commission's site at cpsc.gov before you buy, and register the unit with the maker so they can reach you if there's a problem.

Where he is wrong

Grandma reheated leftover pizza in theirs one Sunday night. Crisp bottom, melted top, done in a few minutes. Grandpa took one bite, set the slice down and stared at the microwave the way you'd look at an old friend who'd been lying to you for decades. He hasn't microwaved a slice since. She was right, and he's said so in front of witnesses.

He concedes the rest with grace:

• Leftovers come back to life. Fries, wings, roasted vegetables and fried chicken get crisp again instead of going limp.
• It's fast. A small chamber heats in a few minutes, so a weeknight side doesn't mean waiting on a full-size oven.
• It doesn't cook the house in July. All that heat stays in a box on the counter.
• For small batches it usually takes less energy than heating a big oven for one tray of food.
• Frozen food is better in it. Fish sticks, tater tots and frozen fries come out crunchier than they do on a sheet pan.

One rule he wants on the record. Crisp on the outside tells you nothing about the inside. Cook chicken to 165°F and check with an instant-read thermometer. Your eyes aren't a thermometer.

The verdict

Worth it, with conditions.

It's for households of one to four, people who live on leftovers, anybody whose freezer is mostly things that come in bags, and kitchens that turn into saunas every summer. If you cook for a crowd every night and your oven works fine, you may not need one. Look at a convection toaster oven with an air fry setting instead. It does the same job, holds more and still makes toast.

Three things to check before you buy:

1. Capacity and footprint. Match the quarts the maker lists to how many people you feed. Then measure your counter, including the clearance the manual asks for around the vent.
2. The basket. Find out what it's coated with, whether it's dishwasher-safe and whether replacement baskets and trays are sold. That part wears out first.
3. The warranty and the recall list. Read the actual warranty document for length, parts versus labor, what voids it and who pays shipping. Then search the model number at cpsc.gov.

Check the current price, and put it side by side with a convection toaster oven before you decide.

Grandpa owns one now. He still calls it the drawer. And every so often, when he thinks nobody's watching, he checks underneath it for the oil.