An illustrative example embodiment of an elevator system includes: a plurality of elevator cars; a plurality of elevator machines, respectively associated with the elevator cars to selectively cause movement of the associated elevator car, at least some of the elevator machines respectively operating in a first mode including consuming power and in a second mode including generating power; a power source having a power output threshold and a power intake threshold; and at least one controller that is configured to determine when the power source is providing power for the elevator system, and dynamically adjust how the plurality of machines move the elevator cars to maximize a number of the plurality cars being used to move passengers while keeping power consumption by the elevator system below the power output threshold and keeping power generation by the elevator system below the power intake threshold.