Power Reserve is a feature found on some high-end watches that allow the wearer to know how much power is left in the watch movement before it needs to be manually wound. It gives the wearer an indication of how much time they have left before they need to wind the watch again. The power reserve feature is typically indicated by a small sub-dial and is measured in hours or days. The power reserve feature is useful for those who want to keep track of their watch’s power level and helps ensure that their watch does not stop unexpectedly.