Hong Life CalculatorsUnderstanding the oven, air fryer and microwave cost calculator — concept and principle
Cooking appliances use a lot of power for short periods, so their running cost is easy to guess wrongly. This calculator estimates the monthly and yearly electricity cost of an electric oven, air fryer, microwave or hob from its power, average daily cooking time and your electricity price, which helps when you choose which appliance to use for everyday meals.
How it is calculated
- kWh per month = W ÷ 1000 × hours per day × days per month
- Monthly cost = kWh per month × price per kWh
- Yearly cost = monthly cost × 12
Hours per day is the average cooking time, so 30 minutes is 0.5 and 20 minutes is about 0.33. For W, use the appliance's rated input power. Microwaves often advertise their cooking (output) power, for example 800 W, while the input power printed on the rating plate is noticeably higher; enter the input figure.
The principle
Energy is power × time; the meter bills kWh. An oven heats a large insulated box and its air before the food gets hot, then its thermostat cycles the elements to hold temperature, so the average draw after preheating is below the rated power. An air fryer heats a much smaller space and blows hot air quickly over the food, so it usually reaches temperature faster and needs less total time. A microwave heats the water in the food directly. Because cost depends on power and time together, a lower-wattage appliance is only cheaper if it does not take much longer.
Worked example
- Inputs: 1,500 W, 0.5 hours per day, 30 days, $0.25 per kWh.
- Power in kW: 1,500 ÷ 1,000 = 1.5 kW.
- Monthly energy: 1.5 × 0.5 × 30 = 22.5 kWh.
- Monthly cost: 22.5 × $0.25 = $5.625, shown as $5.63.
- Yearly cost: 22.5 × $0.25 × 12 = $67.50.
| Power (W) | Monthly cost |
|---|---|
| 375 | $1.41 |
| 750 | $2.81 |
| 1,125 | $4.22 |
| 1,500 | $5.63 |
| 1,875 | $7.03 |
| 2,250 | $8.44 |
| 3,000 | $11.25 |
How to read the result
The result is an upper estimate at full power. To compare appliances for the same dish, run the calculation for each with its own power and cooking time, then compare. Small portions usually favour the microwave or air fryer; a full oven cooking several dishes at once spreads its preheat energy over more food. Skipping unnecessary preheating and keeping the door closed also cut oven energy.
Common mistakes
- Using a microwave's output power instead of its input power.
- Forgetting preheating time for the oven.
- Assuming a lower-wattage appliance is always cheaper.
Frequently asked questions
Is an air fryer cheaper than an oven?
For small portions usually yes, because it heats a smaller space and cooks faster. Compare both here with your own times.
How much does it cost to run a microwave for 5 minutes?
Input kW × 5/60 h × price. A 1.2 kW input microwave at $0.25 per kWh costs about $0.025.
Does a fan oven use less energy?
Moving air transfers heat faster, so you can often cook at a lower temperature or for less time.
Sources: International System of Units (SI), BIPM · U.S. Department of Energy, Energy Saver — cooking appliances