A microwave is the cheapest way to cook at the October 2026 price cap, for anything it can cook. A jacket potato costs about 4p in a microwave, about 10p in an air fryer and about 29p in an electric oven. The slow cooker is the surprise. On the one metered comparison we could find, it used two and a half times the energy of an oven to cook the same cottage pie.
Those figures use the Ofgem cap for 1 October to 31 December 2026: 26.32p per kWh for electricity, paid by direct debit. We worked them out on 2 October 2026 from published energy measurements, not from the wattage printed on the box. We also read the 30 best selling microwave listings on Amazon UK the same day. Not one of them tells you how much electricity the microwave draws.
Key findings, 2 October 2026
- A jacket potato costs about 4.0p in a microwave, 10.3p in an air fryer and 28.5p in an electric oven at 26.32p per kWh.
- The air fryer and oven figures are Which?’s lab measurements, preheat included. Which? still prices them at the old July to September rate.
- A slow cooker on low for 10 hours used 1.32 kWh, or 34.7p. An oven cooked the same cottage pie for 0.53 kWh, or 13.8p.
- Of 30 best selling microwave listings, 20 print a “Power Consumption” figure. In 19 it is the cooking output copied down, and the other is lower than the output. We call this the consumption copy-down.
- Samsung’s own spec sheet gives its MS23K3513AK a consumption of 1,150W. Its Amazon listing says 800 watts.
- Wattage times minutes overstates an oven by 2.5 times and an air fryer by 2.9 times, because their thermostats switch the element off. We call this the nameplate overcount.
What each appliance costs per cook
The only fair test is the same food in each appliance. A jacket potato is the one dish all of them cook, and it is the one with published energy figures for three of the four.
| Appliance | Energy per cook | Cost per cook | A year | Where the figure comes from |
|---|---|---|---|---|
| Microwave (Samsung MS23K3513AK, 800W) | 0.153 kWh | 4.0p | £4.20 | Samsung’s 1,150W consumption figure, times 8 minutes at full power for a 350g potato (British Dietetic Association recipe) |
| Air fryer (Morphy Richards Health Fryer 480003, 1,400W) | 0.392 kWh | 10.3p | £10.73 | Which? lab measurement, about 200g potato, 48 minutes with preheat |
| Electric oven (Bosch Serie 2 HHF113BR0B) | 1.084 kWh | 28.5p | £29.67 | Which? lab measurement, about 200g potato, 68 minutes with preheat |
The microwave figure is for a potato nearly twice the size of the one Which? used, so if anything it flatters the air fryer and the oven. We left the slow cooker out of this table. Slow cooker jacket potatoes are a real recipe, but we found no published energy figure for one.
Which? measured three more foods in the same air fryer and oven. Here they are at the October cap.
| Food | Air fryer | Electric oven | Air fryer saves |
|---|---|---|---|
| Roast chicken, 1.3 to 1.4kg | 0.54 kWh, 14.2p | 1.157 kWh, 30.5p | 16.2p |
| Jacket potato, about 200g | 0.392 kWh, 10.3p | 1.084 kWh, 28.5p | 18.2p |
| Frozen chips, 320g | 0.287 kWh, 7.6p | 0.863 kWh, 22.7p | 15.2p |
| Three-egg sponge cake (smaller in the air fryer) | 0.223 kWh, 5.9p | 0.71 kWh, 18.7p | 12.8p |
The slow cooker gets its own comparison, because the dish it is built for is a stew or a pie for the family, not a potato.
| Appliance | How long | Energy | Cost per cook |
|---|---|---|---|
| Slow cooker on low (Morphy Richards Accents Sear and Stew 3.5L) | 10 hours | 1.32 kWh | 34.7p |
| Slow cooker on low, cut to 8 hours (our estimate at the same average draw of 132W) | 8 hours | 1.06 kWh | 27.8p |
| Electric oven at 180°C, warm-up included | 1 hour | 0.53 kWh | 13.8p |
Why the microwave wins
Time. A microwave draws more power than you would guess from the box, 1,150W for Samsung’s 800W model, but it only runs for eight minutes. The air fryer runs for 48 minutes and the oven for 68, and both spend part of that heating up their own metal and air before the food gets anything.
The catch is the result. A microwaved potato has soft skin. Plenty of people microwave a potato for most of its time and finish it in an air fryer or oven for the skin, which puts the cost somewhere between the two rows. We have no measured figure for that split, so we have not priced it.
The slow cooker surprise
Slow cookers have a reputation as the cheap way to cook, and their wattage is small. The Morphy Richards in the table is rated at around 130 to 163 watts. The problem is the hours. Ten hours at an average of 132W is 1.32 kWh. The oven pulled far more power, but for one hour, and once it was up to 180°C its thermostat kept switching the element off. It finished on 0.53 kWh.
One home test is not a lab study, and it was done with one slow cooker and one oven. But the Smart Energy GB figure for a slow cooker, 1.3 kWh a meal, matches it closely, and the arithmetic is hard to argue with. Cooking a pie in the slow cooker once a week instead of the oven costs about 21p a time, or £10.88 a year, at the October cap.
That is not a reason to throw your slow cooker out. Dinner ready when you walk in the door at 6pm is worth something, and cheap tough cuts need the long cook. It is a reason not to buy one to save on your bill.
What the microwave listings tell you
To price a microwave you need the electricity it draws, its input power. The number on the box, such as 700W or 800W, is the cooking output. Some of the electricity is lost as heat inside the microwave on the way, so the input is always higher. Samsung puts the gap for its MS23K3513AK at 800W out and 1,150W in.
We read the 30 microwaves in Amazon UK’s Solo Microwaves best seller chart on 2 October 2026, taking the title, the bullet points and the product details table on each listing.
| What the listing does | Listings, of 30 |
|---|---|
| Prints a “Power Consumption” figure in its product details | 20 |
| of which the same number as the cooking output | 19 |
| of which lower than the cooking output (700 against 800 watts) | 1 |
| of which higher than the cooking output, as a real input figure would be | 0 |
| Prints no consumption figure at all | 10 |
| States what a cook costs, in pence or kWh | 0 |
We call this the consumption copy-down: the output figure copied into the box where the input belongs. It is not a small error. If you trusted the Samsung listing’s 800 watts, you would price our jacket potato at 2.8p. Samsung’s own figure makes it 4.0p, 44% more. The microwave is still the cheapest way to cook a potato either way, but a listing’s “Power Consumption” line is not a number you can do sums with.
Samsung was the only maker in the top 30 whose own published specification we found giving a consumption figure. The number one, Russell Hobbs’ RHM2076B, gives only a rated output of 750 to 800W in its instruction manual.
The nameplate overcount
Most running cost guides, including some of our own older pages, work out a cooking cost as wattage times time. That works for a microwave on full power and for a slow cooker on low, which run more or less flat out. It does not work for an oven or an air fryer, because both use a thermostat that switches the element off once they reach temperature.
| Appliance | Rated power | Time | Wattage times time | Measured | Overcount |
|---|---|---|---|---|---|
| Bosch Serie 2 HHF113BR0B oven | 2.4kW | 68 min | 2.72 kWh, 71.6p | 1.084 kWh, 28.5p | 2.5 times |
| Morphy Richards 480003 air fryer | 1.4kW | 48 min | 1.12 kWh, 29.5p | 0.392 kWh, 10.3p | 2.9 times |
We call this the nameplate overcount. It is why so many guides tell you an hour of oven costs 50p or more when a measured hour at 180°C, warm-up included, came to about 14p. It also explains why the slow cooker looks cheap on paper. Its wattage times time is close to the truth, while the oven’s is two or three times too high, so the comparison is rigged before it starts.
Is an air fryer worth buying to save on the oven?
Only if you cook small amounts in the oven often. We use a simple test, the pence-back point: the price of the appliance divided by what it saves per cook. The Tower Vortx 4.2L air fryer below is 1,400W, the same rating as the air fryer Which? measured, and cost £39.99 on 2 October 2026.
- Jacket potatoes, saving 18.2p each: it pays for itself after about 220.
- Portions of frozen chips, saving 15.2p each: after about 264.
At chips twice a week that is about two and a half years. The saving disappears for a full oven. An air fryer basket holds one or two portions, and a Sunday roast for six that needs two or three batches can cost more in an air fryer than in one oven run.
What we could not price
A gas oven burns gas at 7.97p per kWh, less than a third of the electricity price, but we found no published measurement of how much gas one uses for a given dish, so we have not put a figure on it. The same goes for every kind of hob. And we found no measurement of how an oven’s energy rises with the amount of food in it. Cooking several potatoes at once is the case most likely to narrow the oven’s gap, but we cannot put a number on it.
How we worked this out
Every cost on this page is a published energy figure in kWh multiplied by 26.32p, the Ofgem cap rate for electricity from 1 October to 31 December 2026, and rounded to one decimal place at the end. The air fryer and oven energy comes from Which?’s laboratory tests, which include preheating. The slow cooker and oven pie figures come from Ben Tasker’s smart plug measurements, published on 14 October 2022. The microwave figure is Samsung’s published power consumption of 1,150W times eight minutes, the full-power time the British Dietetic Association gives for a 350g potato in an 800W microwave. A microwave on full power runs its magnetron continuously, which is why wattage times time is fair for it. Standing charges are left out, because you pay them whether you cook or not.
We have not cooked anything on a meter ourselves. This is desk research, and each figure comes from one appliance. Yours will differ with the model and with how full you load it. Our appliance running cost calculator does the same sum for heating appliances, and the UK running cost index covers the rest of the house.
Our picks
Prices are what Amazon UK showed on 2 October 2026. If you buy through these links we may earn a commission, which does not change what you pay.
Samsung MS23K3513AK 23L solo microwave, 800W
£125. About 4.0p for a jacket potato at the October cap. It is the one microwave in the top 30 whose maker publishes what it draws, 1,150W, so its running cost is the one we can actually work out rather than guess. Number 6 in Amazon UK’s Solo Microwaves chart on 2 October 2026.
The catch: it costs more than twice as much as the cheapest microwaves in the chart, and the saving per cook is fractions of a penny between one microwave and another. If you already own a working microwave, the cheapest way to cook is to use it more, not to replace it. Its own Amazon listing still prints 800 watts as its power consumption.
See it on AmazonTower T17147 Vortx 4.2L air fryer, 1,400W
£39.99. The same 1,400W rating as the air fryer Which? measured, which cooked a potato for 10.3p against the oven’s 28.5p. At that saving it pays for itself after about 220 jacket potatoes. Number 5 in Amazon UK’s Air Fryers chart on 2 October 2026.
The catch: 4.2 litres is one basket, enough for two people. Feed a family in batches and the saving shrinks fast. The same wattage does not guarantee the same kWh as the Morphy Richards, because no air fryer maker publishes a measured figure.
See it on AmazonMorphy Richards Accents 3.5L Sear and Stew slow cooker
£39.99. From the same range as the slow cooker in the metered pie test, and the pot goes on the hob, so you brown the meat in it and save a pan. Put dinner on at 8am and it is ready when you get in.
The catch: on that test it cost 34.7p for a pie the oven did for 13.8p. Buy it for the time it saves you, not the electricity. The test unit was bought in 2022, and we cannot confirm this listing draws exactly the same.
See it on Amazon
As an Amazon Associate I earn from qualifying purchases. (paid link)
The table above pulls live prices from Amazon’s product feed, which can sit a few pence away from the price on the product page. The prices in our text are the ones we saw on the product pages.
Skip this
Who should not buy a new appliance to cut cooking costs
If you already own a microwave, use it for more of your cooking before you buy anything. If you cook for four or more most nights, a full oven is often cheaper per portion than an air fryer run in batches. And if your plan is to save money with a slow cooker, the one metered test we found says it will cost you more, not less. The Energy Saving Trust puts all kitchen appliances, kettle and hob included, at around 4% of a typical energy bill, so the pounds at stake are small.
Cheapest way to cook: your questions
What is the cheapest way to cook in the UK?
A microwave, for food it can cook. A jacket potato costs about 4.0p in a microwave at the October 2026 cap of 26.32p per kWh, against 10.3p in an air fryer and 28.5p in an electric oven. For a family pie or stew, an electric oven came out cheaper than a slow cooker on the one metered comparison we found.
Is a slow cooker cheaper to run than an oven?
Not on the measurements we could find. A slow cooker on low for 10 hours used 1.32 kWh, 34.7p at the October cap, to cook a cottage pie that an oven at 180°C cooked in an hour for 0.53 kWh, 13.8p. The slow cooker draws little power, but for many more hours.
Is an air fryer cheaper than an oven?
For small amounts, yes. Which?’s lab tests put a jacket potato at 0.392 kWh in an air fryer and 1.084 kWh in an oven, which is 10.3p against 28.5p at the October cap. For a big meal cooked in several batches the gap narrows or reverses.
How much does a microwave cost to run?
Multiply its input power, not its cooking output, by the minutes. Samsung’s 800W MS23K3513AK draws 1,150W, so eight minutes costs about 4.0p at 26.32p per kWh. Most Amazon listings print the output figure as the power consumption, which understates the cost.
Why do some guides say an oven costs 50p or more an hour?
They multiply the oven’s rated wattage by the time. An oven’s thermostat switches the element off once it is hot, so that overstates the real use. For one Bosch oven, wattage times time came to 2.5 times the energy Which? measured.
Related on Look Into
- Best air fryers UK, with the energy saving claims on 50 listings checked
- Best slow cookers UK
- Cheapest way to dry clothes
- All our running cost head-to-heads
Sources
- Ofgem, energy price cap unit rates and standing charges (1 October to 31 December 2026)
- Which?, air fryer vs oven: energy cost and cooking results compared (laboratory kWh for four foods)
- Ben Tasker, is a slow cooker more energy efficient than an oven? (smart plug measurements, 14 October 2022)
- Samsung UK, MS23K3513AK specifications (output 800W, power consumption 1,150W)
- British Dietetic Association, microwave jacket potato recipe (350g potato, 8 minutes, 800W)
- Russell Hobbs, RHM2076 instruction manual (rated output 750 to 800W)
- Currys, Bosch Serie 2 HHF113BR0B specification (2.4kW)
- Morphy Richards, Health Fryer 480003 (1,400W)
- Smart Energy GB, energy saving in the kitchen (slow cooker 1.3 kWh per meal)
- Energy Saving Trust, top five energy consuming home appliances (updated 3 August 2026; kitchen appliances about 4% of a bill)
- Amazon.co.uk Best Sellers in Solo Microwaves, ranks 1 to 30, read in full on 2 October 2026