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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?

PJTraill
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4 Answers4

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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.

Fred
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  • 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 08 '15 at 02:29
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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 08 '15 at 02:37
  • @PJTraill yes, the amount specified by the manufacturer and indicated by the markings on the side. – Ⴖuі Dec 11 '15 at 21:22
  • If you have gas stove, consider using that instead. Unless your electricity is from renewable sources, it is more efficient to generate heat from natural gas and not electricity. – Tomáš Zato Nov 21 '19 at 15:27
  • @TomášZato: But does the kettle not transfer heat to the water with lower losses? I always assumed quite a lot of heat from a gas cooker went into the air. – PJTraill Oct 10 '23 at 21:35
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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.

Highly Irregular
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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.

Chris H
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  • While that is a good point about the sensor, one could always avoid that problem by turning it off manually (as also suggested in Highly Irregular’s answer: https://sustainability.stackexchange.com/a/4892/2828). – PJTraill Oct 10 '23 at 21:30
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The mark is to prevent overflow when the water boils. Be careful as the water that overflow may leak down. Depending on the kettle design, the water may even touch the connection base where there's electric plate exposed and might cause accidents. If the base is just fine with no potential for exposure to water in any way, then it probably is okay to go pass the line a little bit. However, the next risk is the splashing of the boiling water. You won't want to be near it when it reaches boiling point.

Choosing a good kettle design is important for this. Make sure it is approved to be safe by your government as well. Electronics usually have to pass through some tests to ensure safety. So, this is something to look at rather than choosing a China brand kettle just because it's cheaper. Not saying all is bad just something to consider.

aling savvy
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    Welcome to Sustainable Living! Your answers seems to discuss the issues of going over the maximum mark, but the question is about staying below the minimum mark. – THelper Dec 28 '21 at 10:09
  • Note that the brand (Moulinex) is European, even if it is made in China. – PJTraill Oct 10 '23 at 21:36