Which feature helps users save battery life on their Mac?

Low Power Mode is a feature specifically designed to extend battery life on Mac devices. When activated, it reduces the overall energy consumption by limiting background activities, reducing the brightness of the display, and optimizing system performance. This helps to preserve battery life, particularly in situations where users may not have immediate access to a power source and need their device to last longer.

The other options, while beneficial in their own right, do not directly focus on battery preservation in the way Low Power Mode does. For instance, features like Night Shift reduce blue light exposure for user comfort but do not impact power consumption significantly. Similarly, auto-brightness adjusts screen brightness based on ambient light but doesn't offer the comprehensive battery management capabilities of Low Power Mode. Faster CPU speed, on the other hand, generally consumes more power, making it counterproductive for battery conservation. Thus, Low Power Mode is the most effective choice for users looking to extend the battery life of their Mac.