Quick answer: For a single meal, the microwave is cheapest (about 0.11 kWh, $0.02 in the US or 2.9p in the UK), then the air fryer (about 0.5 kWh), the slow cooker (about 1.2 kWh) and the electric oven (about 1.4 kWh including preheating). The oven catches up when you cook a lot of food at once.
What matters is energy, not power: a microwave draws over 1,000 W but runs for minutes, while a slow cooker draws little but runs for hours. Here is what each typical meal uses.
Cost per meal compared
| Appliance and use | Energy per meal | US per meal | US for 20 meals | UK per meal | UK for 20 meals |
|---|---|---|---|---|---|
| Microwave, 6 minutes (about 1,100 W input) | 0.11 kWh | $0.02 | $0.40 | 2.9p | 58p |
| Air fryer, 20 minutes (1,500 W) | 0.50 kWh | $0.09 | $1.82 | 13p | £2.63 |
| Slow cooker, 6 hours on low (about 200 W) | 1.2 kWh | $0.22 | $4.37 | 32p | £6.32 |
| Electric oven, 10-minute preheat plus 40 minutes (2,500 W) | 1.4 kWh | $0.25 | $5.10 | 37p | £7.37 |
The oven figure is an estimate: 2.5 kW for a 10-minute preheat (about 0.42 kWh) plus 40 minutes with the element on about 60% of the time (about 1 kWh).
When each appliance makes sense
- Microwave: reheating, steaming vegetables, cooking small portions. Nothing is cheaper for a single bowl of food.
- Air fryer: crisping and roasting one to three portions. No long preheat and a small space to heat.
- Slow cooker: stews and cheaper cuts. It uses more energy than an air fryer, but replaces hours of hob or oven cooking.
- Electric oven: large batches, roasts and baking several trays at once. Fill the oven and the cost per portion falls.
Tips that apply to all of them
- Cook with the lid on or the door closed; every opening lets heat escape.
- Batch cook and reheat portions in the microwave.
- Switch the oven off a few minutes early and let residual heat finish the job.
Check your own appliance
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Frequently asked questions
Is an air fryer cheaper than an oven?
For small meals, yes: typically around a third of the energy. For a large batch that fills the oven, the difference per portion shrinks.
Is a slow cooker expensive to run?
No. At around 200 W on low, six hours uses about 1.2 kWh, $0.22 in the US or 32p in the UK.
A real example: one week of dinners
Suppose a two-person household cooks seven dinners a week. If every dinner uses the electric oven (about 1.4 kWh), that is 9.8 kWh a week, about $1.78 in the US or £2.58 in the UK. Moving four of those dinners to the air fryer (0.5 kWh each) and reheating two in the microwave (0.11 kWh each) brings the week down to about 3.6 kWh: roughly $0.66 or 95p.
Over a year that switch is worth around $58.49 in the US or £84.58 in the UK, without changing what you eat.
Choosing the right appliance for the job
- Microwave: reheating, steaming vegetables, porridge, baked potatoes (finish in the air fryer for crisp skin).
- Air fryer: small portions that need browning or crisping: chips, chicken pieces, roasted vegetables.
- Slow cooker: stews, chilli, pulled meat and soups for several portions.
- Oven: large roasts, baking, and batch cooking several dishes at the same time.
More questions readers ask
Is a combination microwave worth it?
A combination microwave with a grill and convection mode can replace the oven for small meals, which helps in small kitchens and households.
What about a gas oven?
Gas costs less per kWh than electricity, so a gas oven usually costs less per hour, but it still heats a large space and is less efficient for small portions than an air fryer.
Sources
- U.S. Energy Information Administration, Short-Term Energy Outlook.
- Ofgem, Energy price cap.
- Our methodology.