Power Reserve

The power reserve of a mainspring-driven mechanical watch or clock generally refers to the amount of time the timekeeping instrument can run autonomously. When provided in the specifications of a watch, the power reserve refers to its capacity after it has been fully wound. In other words, it is the total running time of the watch in between successive windings.

While mechanical spring-driven clocks typically have seven days of power reserve, those in mechanical wristwatches generally have between 36 and 48 hours.

Even longer power reserves can be found in high-end complication watches such as the Patek Philippe Gondolo 10 Day Power Reserve Ref. 5100J-001 and Jaeger-LeCoultre’s Reverso Grande Date 8 Days.

When worn, the power reserve of an automatic or self-winding movement will be extended and continue running as long as one’s wrist movements cause the winding mechanism, the oscillating weight or rotor, to wind the mainspring. The power reserve will also be maintained if placed and rotated in a watch winder. Conversely, if the wristwatch is left unattended for a long period, on a table for example, its power reserve will gradually be depleted.

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