Water level indicator
A device that allows you to estimate the amount of water in the kettle without opening its lid. Most often
the water level indicator has the form of a scale applied either to the transparent wall of the container, or to a transparent insert in an opaque wall. In any case, this function allows you to measure the volume of filled water quite accurately, and not just determine it “by eye”. This possibility is especially important for models with open coils (see "Heating element"), in such devices, a mark on the indicator is usually applied to the minimum allowable water level.
Opening the lid with a button
Kettles (see "Type") in which the lid opens at the touch of a button. This opening is faster and more convenient, and often safer than the traditional way (grab the lid and pull it up): the lid can get quite hot when the kettle is in operation, and long contact with it is fraught with burns. And although the button can also be placed on the lid, a short press is enough to activate it, and even in such cases the risk of getting burned is minimal. On the other hand,
opening the lid with a button complicates the design of the kettle and reduces its reliability.
Double-walled
Double-walled are found mainly among traditional electric kettles.
This design performs several functions at once. First of all, it significantly improves thermal insulation, allowing the kettle to retain heat longer and save energy when heating. Also, double-walled increase strength and reliability — it is more difficult to break through such a wall or noticeably damage it than a single one. And in some models, the outer side is made of plastic, and the inner side is made — of metal; this allows you to combine the advantages of both materials without a significant increase in cost.
