What are the main differences between the heating method of an air fryer and an oven or microwave

Heating principle of air fryer: rapid hot air circulation technology
The air fryer uses rapid hot air circulation technology (Rapid Air Technology). Through the built-in heating device and powerful fan, the air is quickly heated to the set temperature, and then circulated to the surface of the food in a high-speed airflow. The hot air evenly surrounds the food in the closed cavity, thereby achieving the effect of cooking and dehydration.
This method belongs to convection heating, which mainly relies on air flow to carry away heat energy. In contrast, the heat transfer efficiency of the air fryer is higher, and the heat is concentrated on the surface of the food, so that it is quickly dehydrated to form a crispy crust, similar to the effect of frying, but the fat intake is greatly reduced.

The heating principle of the oven: a combination of radiation and natural convection
The heating method of the oven mainly relies on the electric heating tube or gas heating element to release infrared radiation heat, and cooperates with the hot air convection naturally formed in the cavity for cooking. Some high-end ovens are equipped with fans to realize the "hot air circulation" function, but the overall heating speed is still relatively slow.
The heat conduction in the oven is mainly based on "radiant heat + natural convection", the temperature rises slowly, and the heat distribution is not as uniform as that of the air fryer, especially when the hot air mode is not turned on. It is suitable for slow heating, baking or baking cakes, bread and other ingredients that need to be cooked internally.

Heating principle of microwave oven: microwave medium vibration heating
Microwave ovens use high-frequency electromagnetic waves (usually 2450MHz microwaves) to stimulate the high-speed vibration of food molecules (mainly water molecules), thereby generating heat through friction. This heating method does not rely on air or surface heat sources, but converts electromagnetic energy into heat energy inside the food to directly heat the molecular structure.
Microwave ovens heat quickly and are suitable for thawing, heating, and reprocessing cooked food, but are not suitable for dishes that pursue crispy or baked effects on the surface. Because its heating process depends on the water content of the food, the heating uniformity is poor, and common phenomena include local overheating or undercooked center.

Practical application differences between air fryers and ovens
Air fryers are significantly better than traditional ovens in preheating time. Most air fryers can reach the set temperature within 3 minutes, while ovens usually require more than 8-15 minutes of preheating time. Air fryers are suitable for daily quick preparation of small portions of fast food such as French fries, chicken wings, fried chicken nuggets, shrimps, etc.
Ovens are more suitable for large-volume, high-humidity baked foods, such as cakes, pizzas, whole chickens, roasted ribs, etc. Because of its large cavity space and slow heating, it can gradually penetrate the heat into the food, and it is not easy to have the problem of burnt outside and raw inside.
In terms of the degree of restoration of ingredients, air fryers are closer to frying, with obvious crispy crust, while ovens tend to have a baking taste, with a slightly dry surface but full of fragrance.

Differences in cooking goals between air fryers and microwave ovens
Air fryers are suitable for "making" food, that is, cooking raw ingredients into an edible state, with functions such as dehydration, carbonization, and coloring, simulating frying but without a lot of oil.
Microwave ovens are more suitable for "processing" food, such as thawing, heating, and reprocessing, and lack carbonization function. If you want a crispy outer skin, the microwave oven needs to be heated with the grilling mode or the baking tray, which is still not as stable as the air fryer.

Differences in heating speed and energy consumption
The heating speed of air fryers is in the middle, usually faster than ovens and slower than microwave ovens. A typical air fryer takes about 15 minutes to cook chicken wings at 200°C, while the same ingredients only take 5 minutes in a microwave and 20-25 minutes in an oven.
In terms of energy consumption, microwave ovens are the most efficient, with the largest heat output per unit of energy consumption; air fryers are second, because of their small cavity and concentrated heat energy; ovens have the lowest energy efficiency due to their large space and high heat loss.

Comparison of food taste and surface treatment capabilities
Due to the wide contact area of high-temperature airflow, air fryers have significant surface dehydration and coloring capabilities, and can achieve a golden and crispy crust effect. They are the closest oil-free equipment to simulate frying.
The surface treatment effect of ovens is second, and caramelization and Menard reaction can also be formed under high temperature conditions, but the speed is slow and the time required is long.
Microwave ovens have almost no caramelization ability, and surface treatment relies on additional auxiliary functions or special utensils, such as grills and crispy boxes.