A variable-temperature kettle is an electric kettle designed with a mechanism for controlling the temperature of the water. Users of a variable-temperature kettle can set the kettle to heat water to a desired temperature. Brewing kettles can use different mechanisms for setting water temperature, including a digital thermostat, a knob controller or a push-button pad. In general, variable-temperature kettles are more expensive than standard electric kettles but are often in demand amongst tea and coffee connoisseurs because careful brewing of these beverages often requires heating water to a temperature below boiling.
A standard electric kettle typically heats water to boiling. Those who need water at a lower temperature have two options: the first is to simply heat the water to boiling and then allow it to cool down until it reaches the desired temperature. The other method is to try to gauge at which point the heating water has reached the appropriate temperature and the kettle can be turned off. Both methods require that the user pay a great deal of attention to the water and kettle. They also require the user to test the water with a thermometer.
With a variable-temperature kettle, the user does not have to babysit the kettle in order to get water at a particular temperature. The most precise, and often most expensive, kettles are those that allow users to set the exact temperature using a digital thermostat. Another option is a variable-temperature kettle with preset temperatures that can be selected using a knob controller or by pushing a button. Finally, there are some kettles that simply have a knob controller that allows the user to select a temperature ranging from cool to boiling, though the controller may not permit the user to select a specific temperature.
The value of each type of variable temperature kettle largely depends on the intended use of the kettle. For some people, the option of simply being able to get both warm and boiling water out of the kettle is quite enough for their needs. Serious tea and coffee lovers, however, depend on exact temperatures for extracting optimal flavor from their beverage. In such cases, being able to set a precise temperature or choose from a wide range of temperatures is extremely important. In fact, some tea companies now sell kettles that heat water to the various temperatures best suited for different types of tea, lower temperatures for green and white teas, and higher temperatures for black teas.