What makes this a fair comparison?
Match food quantity and doneness. An air fryer often uses a smaller heated chamber and shorter preheat, but a full oven can be more efficient for large batches or several dishes cooked together.
A calculation you can check
At full rated input, a 1.5 kW air fryer used for twenty minutes consumes at most about 0.5 kWh during that interval. A 2.8 kW oven used for 35 minutes would consume at most about 1.63 kWh if its elements never cycled off. These are upper-bound arithmetic examples, not measured meal results: thermostats cycle, preheating varies and a large meal may need several air-fryer batches.
Before trusting the difference
- Cook the same amount of food to a similar result on both sides.
- Count every batch and any preheat time before comparing energy per meal.
- Use a meter reading for each complete session when the difference matters.
Wattwise reports energy and operating cost only. Purchase price, capacity, comfort, maintenance, expected life, and repairability belong in a replacement-payback scenario.