A rice cooker or rice steamer is an automated kitchen appliance designed to boil or steam rice. It consists of a heat source, a cooking bowl, and a thermostat. The thermostat measures the temperature of the cooking bowl and controls the heat. Complex rice cookers may have sensors and other components, and may be multipurpose . A basic rice cooker has a main body. a cooking container which holds the rice, an electric heating element, and a thermostat.
The bowl is filled with rice and water and heated at full power. The water reaches and stays at boiling point . When the water has all been absorbed, the temperature can rise above boiling point, which trips the thermostat. Some cookers switch to low-power warming mode, keeping the rice at a safe temperature of approximately 65 °C . Simpler models switch off; the rice has entered the resting phase.
More advanced cookers may use fuzzy logic for more detailed temperature control, induction rather than resistive heating, a steaming tray for other foods, and even the ability to rinse the rice. Depending on quantity, it takes about 20 minutes to 1 hour for most electric rice cookers to complete cooking. Some advanced models can back-calculate the cooking start time from given finish time. The time required for cooking rice depends on the amount of rice, the power of the heating elements, and atmospheric pressure, thus it is not constant. Pressure-cooker models are not influenced by atmospheric pressure. The special features distinguish high-end models from lower-cost, simpler models.
Automatic rice cookers may be either gas or electrical appliances. Most dedicated home rice cookers are of the electric type. In commercial or industrial use, there are many varieties, such as large gas or electric rice cookers, a large-scale rice cooker that is called a "rice boiler", and fully automatic versions which handle the whole process of rice cooking from washing rice to the end of the cooking cycle.