In the debate between a kettle and a thermos, the thermos is generally the superior choice for maintaining the temperature of hot beverages. A kettle is primarily designed for boiling water, while a thermos is engineered to insulate and retain heat. According to a study by the Good Housekeeping Institute, thermoses can keep beverages hot for up to 12 hours and cold for up to 24 hours, depending on the material and design. This is due to the vacuum insulation technology used in thermoses, which significantly reduces heat transfer. In contrast, a kettle does not have the same level of insulation and will not maintain the temperature of its contents for an extended period. Therefore, for those seeking to keep their drinks at a consistent temperature throughout the day, a thermos is the clear winner.