Slow cooker against oven, what eight hours on low really costs

Kitchen By Ellen HartwellPublished 28 September 2026

What a slow cooker actually draws

A slow cooker is a heating element wrapped around a ceramic pot with a lid on it, and there is nothing clever inside. Domestic models in the UK run from about 150 watts for a small 1.5 litre pot to 320 watts for a large 6.5 litre one, with 200 watts being the figure most guides use for a family sized cooker.

The low setting does not draw less power than high in most machines. It runs the same element for a smaller fraction of each cycle, which is why the food sits below boiling instead of at a simmer. That matters for the arithmetic, because the number on the plate is the peak rather than the average, and a machine on low may well be pulling its 200 watts for only part of every minute.

Taking the full 200 watts continuously gives you the pessimistic figure, which is the right way round for a cost guide. Whatever your pot does, it will not cost more than this.

Eight hours on low, and every other duration

Two hundred watts is 0.2 kilowatts. Eight hours gives 1.6 kilowatt hours, which at the Ofgem cap rate of 26.11p per kilowatt hour is 41.8p. That is 5.2p for each hour it is on.

The rest of the ladder follows from the same sum. Five hours costs 26.1p. Six hours costs 31.3p. Twelve hours, which is an overnight batch of pulled pork, costs 62.7p. A full 24 hours making stock costs £1.25. A small 150 watt pot takes the eight hour figure down to 31.3p and a large 320 watt one takes it up to 66.8p.

Cooking twice a week comes to 13.9 kilowatt hours a month and £3.62. The cap moves to 26.32p per kilowatt hour on 1 October 2026, which takes the eight hour figure from 41.8p to 42.1p, so nothing in this article changes when the new rate lands.

The old line that a slow cooker uses no more than a light bulb was true when bulbs were 100 watt filaments. Against a modern 8 watt LED the pot uses twenty five times as much, which is still small and is no longer the comparison anyone should be making.

Readers in the United States can run the same 1.6 kilowatt hours against the EIA residential average of 18.34 cents per kilowatt hour, which puts eight hours at about 29 cents and the hour at 3.7 cents.

Rates: Ofgem cap 1 July to 30 September 2026 at 26.11p per kWh (source), EIA residential average June 2026 at 18.34 cents per kWh (source). Checked 2026-09-22.

Against the oven, honestly

The claim you will read everywhere is that a slow cooker costs a fraction of an oven, and it is true for the dishes slow cookers are for. It is not true as a general rule, and the difference matters if you are deciding what to cook rather than which appliance to buy.

The energy label puts a standard fan oven cycle at 0.87 kilowatt hours, or 22.7p, with efficient models down at 0.69 and conventional non fan cooking up at 1.04. On that number alone the oven looks cheap, because a single label cycle is a short standardised test rather than a Sunday roast.

Where the oven loses is duration. A braise that wants four hours at 150 degrees is asking the element to cycle for four hours in a cavity the size of a dustbin, and the slow cooker is doing the same job in a two litre ceramic pot with an insulating lid. The slow cooker finishes the whole eight hours for 41.8p, less than two label cycles. Where the oven wins is anything short and hot, because forty minutes of roasting potatoes is one cycle at 22.7p and the slow cooker cannot produce that result at any price.

The air fryer sits between them. A 25 minute cook at 1,750 watts costs 19.2p, and a halogen oven doing thirty minutes at 1,300 watts costs 17p. For one or two portions of something quick, both beat the slow cooker on both time and money.

Six ways to get more out of a slow cooker

• Fill it between half and three quarters full. An underfilled pot heats mostly air and an overfilled one never gets properly hot in the middle.
• Leave the lid alone. Lifting it drops the temperature by a lot and the machine spends the next twenty minutes putting that back.
• Use low rather than high for anything with connective tissue in it, since cheap cuts are the whole economic case for owning one and they need the long gentle heat.
• Cook two meals at once and freeze one, which halves the electricity per portion without changing the bill at all.
• Brown the meat in a pan first if the recipe asks for it, and accept the extra five minutes of hob. The flavour difference is larger than the two pence.
• Run it overnight if you are on a time of use tariff. Eight hours is long enough to sit almost entirely inside a cheap overnight window.

Is it worth having one

For a household that eats stews, curries, chilli and pulled meat through the winter, a slow cooker is one of very few appliances that saves money and improves the food at the same time. It turns the cheapest cuts in the butcher's counter into the best thing you will eat that week, and it does it for 42p of electricity.

For a household that cooks quick meals for one or two, the case is much weaker. The pot has to be full to be efficient, eight hours is a commitment made at nine in the morning, and an air fryer will feed you for 19p in twenty five minutes.