... The power plant workers generate the same amount of power whether they are at work or not. ... Actually most jobs are like this. Exceptions: Teamsters, Dock workers, Construction, Resource gatherers, Factory workers.
One of J_J's untested assumptions; although here I see he recognizes that Factory production increases when the workers are actually in the building.
Issues about Power Plant Engineers: The amount of power output per employed worker varies. We know from the documentation that it varies based on the individual's experience level. However, a careful observation about presence\absence has not been reported. Following the pattern of the rest of the game code, a more likely assumption is that the output when absent is the same as when present but completely inexperienced; the output when present aligns with the level of experience. Since there are six employees, the variations are so multiple that only serious problems are noticeable. Also, the Engineers are female. If married, they will live close to their husband's job since he chooses the house; and they will take nine months off work for pregnancy from time to time.
Issues about other "indoor" workers: The various service buildings have a variable "throughput" rate which varies based on the experience level of the employees which also is registered in the Service quality rating. The inferential extention of the known use of production code is that the patrons recharge their gages faster when the employees are actually present, with the none present base rate being analogous to the factory, a single completely inexperienced employee.
To assume no variation just is not logical.