Power reserve

What does power reserve mean?

Power reserve is the time a mechanical watch can run after being fully wound, without receiving further energy. The specified duration depends on the movement. A power-reserve indicator shows the remaining reserve, but not all mechanical watches have one.

Specified and measured values

A product description should make clear whether a figure is a manufacturer’s specification or an actual measurement of the particular watch. When testing, record the method, the time of full winding and the time the watch stops. State whether it rested or was worn during the observation.

Running duration and timekeeping accuracy are different measurements. A long running time after winding does not by itself establish how many seconds a watch gains or loses per day.

If the watch has stopped

A mechanical watch may stop because its reserve is exhausted. Follow the instructions for that particular model when winding it again. With an older watch, a possible malfunction should be investigated rather than attributed to power reserve without checking.

See our wristwatches category.

Sources

Longines: power reserve explained and Tissot: restarting after the reserve is exhausted.