The generator was a large hydroelectric generator located in the Pipeworks. The generator is a gigantic turbine, many stories high , and capable of powering the entire city of Ember. It is a major plot element in the first book. Around the year 241, the massive generator begins to reach the end of its operational life and begins to fail at powering the city. It was described to be the size of a house, and the top section contains a control room that can change electricity output and the speed of the turbines.
The generator was created by the Builders during the construction of Ember, and provided electricity to the entire city for nearly 200 year. However, around the year 239, the generator began to experience malfunctions and blackouts were frequent by the year 241. Several blackouts were caused by explosions within the generator, which often caused fires that had to be put out afterwards.
As the river flowed over the two main turbines, the rotation of the waterwheels operated two magnets that created electricity to power the city. The speed of the waterwheels depended on the preset functions in the generator control room, and higher rates of rotation created a higher electrical output, which overloaded many electrical systems.