Electric smokers can be used with either bisquettes or wood chips. The models that use bisquettes offer a very hand’s off experience — you simply load up the machine and let it run. Every time a bisquette burns out, a new one will drop into the chamber. This provides a consistent temperature and controlled level of smoke.
Some electric smokers and all propane smokers use wood chips, which do need to be regularly refilled during the cooking process. Look for models that allow you to reload wood chips without decreasing the temperature or smoke level inside the chamber.