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Watch Complications Explained: The Power Reserve

Modern luxury watches are filled with stunning complications ranging from simple date indications to brilliantly complex moonphases. Features like these – anything other than the ability to tell time – are collectively known as complications. Much more than simple adornments, they elevate the functionality of a watch and even have the ability to change the way we think about watches. For example, can a watch be a calendar? Yes! Thanks to the incredible complexity of the perpetual calendar, some watches will accurately display the day, date, month, and year for hundreds of years without ever needing correction. Incredible! With so many different types of complications available, it helps to understand each one. Join Feldmar as we take a journey to explore the fascinating world of watch complications. 

For our first exploration, let’s check out a beloved and highly useful complication – the power reserve indication! What is a power reserve? Read on to learn more!

seiko prospex snr049

Understanding Power Reserves

The power reserve is a feature sometimes found on watch dials that indicates how long an automatic watch will run before fully winding down. When wound down, an automatic watch ceases to operate until it is rewound.

To understand power reserve indications, it’s important to know that automatic and mechanical watches – by their very design – wind down. In order to tell time and operate, the main spring must be wound tight. In automatic watches, this is simply done by wearing the watch. Your wrist’s motion helps spin the rotor which in turn, winds the main spring. A power reserve indicator on the watch’s dial will show just how much power is remaining before the spring winds down.

Knowing exactly how much “juice” your watch has can be useful if you don’t wear your watch everyday. For example, let’s say you have a watch with a 72 hour power reserve. If you take the watch off your wrist after work on Friday, you can put it back on before work on Monday and it will still accurately show the time. Incidentally,  these watches are sometimes called “weekend-proof” for exactly this reason. Conversely, a watch with a 32-hour power reserve would wind down sometime during the weekend. If you picked it up Monday morning, it would not be running but after a quick winding either by hand or on the wrist and resetting the time, would function properly.

iwc big pilots vegas

Early Days and Beginning

The power reserve was first used in chronometers used in maritime navigation, which John Harrison invented in 1730. Since it’s used for navigation in the high seas, accuracy was paramount in order to prevent maritime disasters. To maintain accuracy, the chronometer spring has to be wound up at all times so it was therefore also necessary to see just how much power remained. If the power level was too low, the chronometer would need to be wound up to maintain accuracy.

Power Reserves in Wristwatches

The first wristwatch with a power reserve was manufactured by Breguet in 1933. However, this was only a single variant. It wasn’t until the 1950s that Jaeger-LeCoultre manufactured wristwatches with power reserves in a series. In these watches, the power reserve was just 6 hours! Today, entry level movements typically offer no less than 32 hours while the world record for longest power reserve is held by the Vacheron Constantin Traditionnelle Twin Beat Perpetual Calendar which can run for a staggering 65 days when fully wound.

zenith defy extreme

Types of Power Reserve Indications

These simple complications come in a surprising array of designs. IWC is famous for incorporating clear and easy to read subdials while Zenith uses a simple line design incorporated into the dial of the Defy Extreme. Seiko has a signature style to their power reserve indications, using an easy to read arc design like the 72-hour reserve on the SNR049 Limited Edition. Finally, Blancpain uses a cleverly placed indication on the back of the Villeret Ultraplate!

Conclusion

A power reserve indication is a simple yet functional feature that adds character to a watch’s dial while enhancing its functionality. A simple glance at the indication will tell you just how much power remains in your watch and whether or not it is time to wind your watch again.

About The Author: Tom Roth

author

Born in Washington state, Tom developed an interest in photography during college at University of San Diego. There, he got started in music journalism, interviewing artists and taking photos at concerts. A life-long tinkerer and collector, it wasn’t long before Tom became fascinated with fountain pens and watches.

Those interests collided in November 2020 when Tom started at Feldmar Watch Company where he lives out every watch geek’s dream: photographing and writing about timepieces. When he’s not tinkering with his watch collection, Tom can be found traveling, biting his nails while watching PNW sports teams, and taking flying lessons.

Read more from Tom Roth

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