This video will explain what is a timepiece power reserve and how to use a power reserve indicator on a watch.
Power reserve is how much stored energy a watch can hold before running out of power. Mechanical watches require the mainspring inside the watch to be wound in order to run. Hand-wound mechanical watches need to have the winding crown manually wound to wind up the mainspring while automatic mechanical watches self-wind thanks to a rotor inside the movement. Depending on the watch, power reserve can range from a little more than one day to over a week.
Certain watches have a power reserve indicator, often called a power reserve display or Réserve de Marche in French. Power reserve indicators are typically located on the dial. They sometimes show how many hours or days are left while others simply include a full-to-empty scale.
Power reserve indicators are particularly useful for manually-wound watches so that the watch can be charged up again before it runs out of juice. Similar to a car gas gauge, when you wind up a manual watch, you can see the arrow on the display moving to the full area. Alternatively, as time passes since the last wind, you can see the arrow on the display moving towards the empty area.
A power reserve display on an automatic watch works the same way as one on a manual watch, however its practicality is evident when the watch is not being worn. It serves to indicate how much time is left before the watch will stop working while it is lying dormant. So prior to the watch’s power reserve running out, you can decide whether to wear the watch, wind up the crown, or store it in a watch winder.
Whenever possible, always refer to the official manufacturer’s instruction manual for more details on how to use the power reserve indicator of your particular watch.