If there is still water after the kettle is electrified for one night, it will be fine, because the kettle will automatically alarm and stop when it boils. If there is no water in the thermos overnight, it will burn out the wires below, cause a failure and cause a fire. Never unplug the thermos after use, it's dangerous. Household appliances, except refrigerators and water dispensers, were unplugged at that time.