The same plate of food can cost wildly different amounts to cook depending on which appliance you reach for. There is no single cheapest one. The microwave wins on small and quick, the air fryer on small and crisp, and the oven on big batches. The waste comes from using the wrong tool for the size of the job, usually firing up a huge oven to warm one dish. This guide puts pence on each appliance at current UK prices and gives you a simple rule for picking the cheapest every time, without buying anything new.
The short answer. For a small portion or reheating, the microwave is almost always cheapest, often under 2p, because it heats only the food. For one or two crisp portions the air fryer beats the big oven, roughly 8p against 30p or more, by heating a tiny chamber fast. The oven is the thirstiest for a small job but the cheapest per portion when it is full, so a roast or a big batch belongs there. Match the appliance to the quantity and you spend the least.
Why the same food costs different amounts
Cooking energy is not really about the food. It is about how much else the appliance has to heat to get the food hot.
A microwave puts energy directly into the food and warms almost nothing else. An air fryer heats a small chamber and circulates hot air tightly around what is in it. A full oven heats a large cavity, the shelves, the door and a big volume of air, and then has to hold all that at temperature for as long as the food cooks, plus a preheat before you even start. The bigger the empty space you are heating, the more you waste on a small dish.
So the cost gap between the three is widest for small jobs and narrowest for big ones. Cook one jacket potato and the oven is wildly more expensive than the microwave. Cook a full Sunday roast and the oven is the cheapest option there is, because that big heated space is doing a lot of work at once. Everything below follows from that single idea.
There is a second, quieter factor: how long the appliance has to stay hot. Cooking time matters as much as power. A 2kW oven that runs for an hour and a half costs far more than the same oven for twenty minutes, because it is holding all that heated space at temperature the whole time. The microwave and air fryer win partly because they finish quickly, so there is less time spent paying to keep anything warm.
What each appliance costs to run
Here are typical power ratings and what a session costs at 26.11p per kWh. Ovens vary, but a domestic electric oven draws around 2 to 2.5kW while heating and cycles on and off once up to temperature, so the figures below assume realistic average draw across a cook rather than full power throughout.
| Appliance | Power | Typical job | Time | Cost |
|---|---|---|---|---|
| Microwave | ~0.8 kW used | Reheat a portion | 5 min | ~1.7p |
| Air fryer | ~1.5 kW | Chips for two | 20 min | ~13p |
| Air fryer | ~1.5 kW | Reheat or small bake | 10 min | ~7p |
| Electric oven | ~2 kW average | Small dish + preheat | 40 min | ~35p |
| Electric oven (full) | ~2 kW average | Roast, several trays | 90 min | ~78p |
At 26.11p per kWh electricity, Ofgem cap July to September 2026. Oven figures assume the element cycles on and off once preheated, so average draw is below the nameplate rating. Worked examples; your appliances and cooking times will differ.
The pattern is clear. Reheating one plate costs about 2p in the microwave and roughly 35p in the oven, a fifteen-fold gap. But spread that 78p ovenful across a roast for six and several side dishes and it is barely 13p a head, cheaper per portion than running three air fryer batches. Put your own appliances and realistic times through the cost calculator to see your gaps in real money.
The microwave: champion of small and quick
For heating a portion, defrosting, or cooking something small, the microwave is almost always the cheapest by a wide margin. It puts energy straight into the food, heats no large cavity, and needs no preheat, so a few minutes of microwaving costs a penny or two.
Its limits are texture and capacity. It will not crisp or brown, and it heats unevenly across a big load, so it is reheating and steaming rather than roasting. But for leftovers, a single serving, softening butter, cooking vegetables or defrosting, nothing beats it on cost. It is also the quiet hero of cutting cooking bills because it does the most common kitchen job, reheating, for almost nothing.
One honest note: the standby clock on a microwave can use more over a year than the cooking does, so switch it off at the wall if it is easy to reach. Our standby power guide covers that quirk.
The air fryer: small meals, crisp results
An air fryer sits between the microwave and the oven. It is really a small, fast fan oven. It heats a tiny chamber quickly and blows hot air around the food, so for one or two portions of something that wants a crisp finish, chips, roast vegetables, a couple of fillets, breaded things, it undercuts the big oven comfortably. No long preheat, far less space to heat.
Its limit is capacity. Cook for a crowd and you are running batch after batch, and three or four batches can use as much energy as one ovenful while taking longer overall. At that point the oven wins again. The air fryer's saving is real but it is pence per meal, not pounds, and only on small jobs. Our dedicated air fryer running cost guide pulls apart the hype and the reality in full.
Treat it as the right-sized tool for small, quick, crisp cooking, alongside the microwave and the oven, not as a replacement for the oven.
The oven: thirsty for a snack, cheapest for a feast
A full-size oven is the most expensive choice for a small job because of all the empty space it heats. Baking one potato in a 2kW oven for an hour is genuinely wasteful. But the oven is not inefficient, it is just big, and that size becomes a strength when it is full.
A whole roast, several trays at once, or a big batch cooked to portion and freeze spreads the oven's energy across a lot of food. Per portion, that is the cheapest way to feed many people. The oven is wasteful when it heats a vast cavity to warm one small dish, and economical when every shelf is working.
You can cut its cost further with a few habits: skip the preheat for anything that does not need it, cook several things at once while it is hot, use the residual heat by switching off a few minutes early, and keep the door shut so you do not dump the heat. Batch-cooking on a Sunday and freezing portions to reheat in the microwave all week is one of the cheapest ways to eat, combining the oven's batch economy with the microwave's cheap reheat.
The simple rule, and where this fits
You do not need to do sums every mealtime. One rule of thumb covers most of it:
- Reheating or one small portion? Microwave. Pennies, every time.
- One or two portions that want crisping? Air fryer. Beats the oven, costs a few pence.
- A big meal, a roast, or batch cooking to freeze? Oven. Thirsty for a snack, but the cheapest per portion when it is full.
Match the appliance to the quantity and you spend the least without owning anything new. The hob has its own place too, especially for boiling and frying, and the induction versus gas hob guide covers that, while the slow cooker earns its keep on long, cheap one-pot meals.
If you want to nail down the numbers for your own kitchen, measure a real appliance with a plug-in energy monitor and feed the result into the running cost calculator. For the bigger picture on cutting electricity use, the main electricity hub gathers it together.