Automatic Watches: Power Reserve and Restarting After Storage

Power reserve answers how long a mechanical watch can run on stored energy. It does not tell you how closely the watch keeps time. Put those two specifications in separate columns when comparing movements.

Automatic winding needs an energy supply

Rolex describes its rotor transferring wrist motion to the mainspring. Its care instructions explain that a stopped watch should be manually wound before use, while running time after removal depends on the model. The page directs owners to the correct model guide for setting details. Read Rolex’s care guidance. Its winding instructions apply to the watches it describes, not automatically to another movement.

Make the reserve figure useful

Imagine putting a fully prepared watch aside at 20:00 on Friday and wearing it at 08:00 on Monday. That gap is 60 hours. A stated 40-hour reserve would not cover it; a stated 70-hour reserve leaves a theoretical ten-hour margin. This is arithmetic based on the claim, not a measured result for a particular watch.

Ask how the figure was obtained

• Which exact calibre and version is installed?
• Is the duration a movement specification or a test of this watch?
• What preparation and operating conditions were used?

For your own run-time record, note the preparation, start and stopping times without resetting the watch midway. Follow its supplied winding instructions. Share the record when discussing a short result; do not diagnose a fault from a specification belonging to a different movement.