Final answer:
The ATX power supply will remain on as needed to meet the power demands of a computer system. The concept can be likened to a house's heating system which operates on a duty cycle to maintain temperature.
Step-by-step explanation:
The duration that an ATX power supply remains on depends largely on its use case scenario. When determining how long a power supply stays active, it's helpful to consider it in the context of an analog, such as a house's heating system, which operates to maintain a specific temperature. Much like a heater, which turns on and off to regulate the temperature, the ATX power supply will also turn on and off according to the demands of the computer system.
For instance, if a heater needs to remain on to maintain the temperature inside a house, it will operate according to its duty cycle. Similarly, an ATX power supply that requires 1,500 W to maintain operations will run as needed to fulfill the power demands of the computer system. If we assume the power supply is either on for 12 hours, or functions at half-power for 24 hours, the duty cycle for maintaining the system's requirements would need to be calculated based on the power draw of the connected components.