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Our electric kettle for boiling water for tea or coffee has what looks like a minimum mark at 0.8 litres (though on closer inspection it says “mini” rather than “min”!). I try to save energy by boiling no more than the amount actually needed for my drink, which is often as little as ca. 0.3 litres, but always enough to cover the base, and have seen no ill-effects so far.

For what it is worth, the kettle in question is a Moulinex Subito made in China rated 2-2.4 kW where the element is concealed under an almost flat stainless steel bottom, but I suspect that pretty much any similar kettle would behave the same way.

Is there any danger in this? If it does depend on the model, what features matter?

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In older kettles with an exposed heating element it does matter. If the element is not covered with water it will overheat and burn out.

With newer kettles without an exposed heating element you may risk reducing the useful life of the kettle as a certain amount of water will be required to absorb and dissipate the heat produced by the heating element.

  • Thanks for this, which is a useful start. Can you be any more concrete about the amount of water needed to dissipate enough heat? – PJTraill Dec 8 '15 at 2:29
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    @PJTraill: That depends on how much power the kettle uses & how much heat the heating element generates. It's why manufacturers place a minimum water level mark on kettles. To boil small amounts of water, for 1 or 2 cups, a travel kettle is an option; their capacity is usually no more than 500-600 mL. – Fred Dec 8 '15 at 2:37
  • @PJTraill yes, the amount specified by the manufacturer and indicated by the markings on the side. – Ⴖuі Dec 11 '15 at 21:22
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I agree with Fred in that it seems logical that a minimum amount of water would be required to help prevent overheating by the element. It's likely though that the manufacturer has specified a fairly conservative minimum amount of water to use.

When using a kettle with a concealed element with less that the minimum recommended amount of water, you could reduce damage that might be caused by overheating by manually switching the kettle off as soon as it boils. You'll save electricity too.

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There's another reason for minimum water levels: when the steam is used to trip the temperature sensor, a certain minimum amount of steam (or rate of steam delivery) is required. This will depend on the contact between the water and the element, so will be more of an issue for exposed elements.

I find that you can get away with quite a bit less than the minimum even with an exposed element, so long as the main part of the element is underwater.

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