What is a watch power reserve?
A power reserve indicator displays the amount of energy left within a mechanical watch. Both automatic and hand-wound watches require winding before they can function, and this is done by winding up a component called the mainspring. The power reserve indicator is usually displayed like a car fuel gauge on the dial and indicates the tension on the mainspring at any moment.
You can find some examples of watches with power reserves here.
Why is a watch power reserve useful?
Owning a watch with a power reserve takes away the guesswork of how long your watch will run before you need to start winding it again. Most mechanical watch owners are aware of their watch’s power reserve which can vary from 38 hours to 80 hours, but the beauty of a power reserve indicator is that you don’t need to make a mental note of every time you wind your watch. Instead, the power reserve indicator does all the work for you.
If you own an automatic watch with a power reserve indicator and you are not wearing your watch, you are able to see how much power is left before the watch will stop running. When the indicator displays the power reserve as low you will know to start wearing the watch again. Meanwhile, if you own a manual-winding watch, the power reserve indicator will let you know when you need to manually hand wind your watch by the crown.
Examples of different power reserve indicators:
The most classic type of power reserve indicator is displayed like car fuel gauge on the dial.
On the Oris Artelier watch below, the power reserve indicator is shown on the non-linear dial at 3 o clock. This watch has a 10-day power reserve and indicates how many days worth of power you have remaining before the watch needs to be powered again. When the small hand gets close to the red section on the gauge, you know it is time to wind up your watch.
Rather than displaying the remaining power in days, some watches like this Junkers Bauhaus watch display the reserve in hours, With a maximum power reserve of 40 hours, the indicator at 12 o clock allows you to see how many hours of power you have left.
Another similar example is this Bell and Ross BR 03 90 watch with a full circle power reserve indicator at 6 o clock. Rather than showing how many hours or days remaining, the indicator just shows how close you are to running low.
Some watches have power reserves that are completely different to these and they can look absolutely stunning. This Nomos Metro Datum 1101 watch boasts a fine example of a unique power reserve indicator. Through the small aparture just off the 12 o clock position, a mint green, white and green feature is used to display the remaining power reserve. When the watch is fully wound, the red part disappears and the aperture is shown as fully white. As the watch slowly uses its power, the red begins to creep back in. Once the white has been fully taken over by the red, the watch has run out of power and needs winding again.
