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Certain complications are already so embedded in our everyday life that we no longer perceive them as complications. The power reserve indicator, or just power reserve for short, is almost as essential to the modern dial of a luxury watch as the battery display on our smartphones. It is a subtle reminder to the owner to wind the watch to prevent it from stopping. Let's take a closer look at the origins, the functionality and modern variations of the power reserve.

  1. What is a power reserve?
  2. The creation of the power reserve
  3. Do automatic watches need a power reserve?
  4. Variations of the power reserve
  5. Watches with a power reserve

What is a power reserve?

Watches with a power reserve show the wearer how much residual energy is left before the movement has to be wound again. If the wearer does not comply with this obligation, the watch stops. The average power reserve varies from about 35 to 48 hours.

How was the power reserve invented?

The power reserve has its origin in the chronometers used for maritime navigation. The indication of latitude and longitude required the highest degree of accuracy, which is why the chronometer spring had to be wound at all times. For this reason, marine chronometers were equipped with a power reserve display that indicated when the spring needed to be rewound. With a deviation of only 0.1 seconds per day, these chronometers were among the most accurate timepieces of their time.

The first wristwatches with a power reserve

The first prototype of a wristwatch with a power reserve on the dial was developed by Breguet in 1933. However, it would take until the 1950s for Jaeger-LeCoultre to offer the first watches with a power reserve produced in series – the Futurematic and later the Powermatic.

A special feature of the Futurematic was that the crown was attached to the back of the case and was only used to adjust the hands. The energy supply was solely provided by kinetic energy. As soon as the watch was put down, the calibre would stop as well. Once the Futurematic was returned to the wrist, it would start again. The power reserve in this model was designed very practically and informed the wearer whether the watch still had the usual six hours of reserve power.

With the Powermatic, Jaeger-LeCoultre finally concentrated entirely on the power reserve following the complication's positive receptions on the Futurematic. While the power reserve was initially only used in luxury watches in the upper price segment, this practical indicator is now also found in entry-level models.

Jaeger-LeCoultre Reverso Grande Date 8 Day Power Reserve Q3008420 240.8.15 watch with steel case and brown leather strap

Do watches with automatic movement need a power reserve?

Simply put, the power reserve display is connected to the winding mechanism by a complex system of wheels and gears and reacts as soon as energy is supplied to it. In most cases, the power reserve is implemented in the form of a differential thread and has a mechanism moving in retrograde in which the hand of power reserve returns to the previous (home) position. Accordingly, the power reserve on the dial is often implemented in the form of a semi-circle.

While the power reserve was originally intended exclusively for watches with manual winding, it has also been used in automatic movements since its development by Jaeger-LeCoultre. Since automatic watches are also driven by the movement of the wrist, a power reserve is not technically necessary. Although the crown on automatic models offers no resistance, the power reserve indicator is a useful tool for keeping track of how much power a watch has left. If the hand should ever completely run down to zero, however, there is no need to panic. Simply set the time and date and wind the watch up again.

Limitless creativity: Variations on the power reserve indicator

If there are indeed limits to the placement of the power reserve, they probably still have to be found. The classic implementation is a separate hand, which is positioned off-centre on the side of the dial and is not connected to the main hands of the watch. However, such a display can take many forms. For example, Panerai offers a horizontal numerical bar in some references of the Luminor 1950 which shows the remaining days. Design legend Alain Silberstein created a model named Legacy Machine 1 for MB&F using three-dimensional power reserve.

Black dial of a Panerai Luminor 1950 PAM00233 watch with 8-days power reserve

Particularly in the upper price segment, people are happy to let their creativity run free. Driven to new heights of performance by its partnership with Ferrari, Hublot designed the MP-05, a model with 11 barrels, a vertical floating tourbillon and a 50-day power reserve displayed on a rotating disc. Another masterpiece of Haute Horlogerie is the U10 Tourbillon Lumière by Angelus that features a power reserve mounted in a narrow display window on the side of the case and shows its power reserve via a simple yet sophisticated full-empty scale. Blancpain also offers another masterwork in watchmaking with its L-Evolution Tourbillon Grande Date Réserve De Marche Sur Masse Oscillante, in which the power reserve is mounted on the rotor itself.

Silver dial of a Cartier Tortue W1542751 2688G watch with power reserve at 6 o'clock

Watch models with a power reserve at Watchmaster

  • The Maurice Lacroix Masterpiece (Ref. MP7078-SS001-120) spreads its power reserve display with a hand across an arc between 1 and 3 o'clock on the dial. The Réserve du marche indicates the status in French: from haut (high) at 1 o'clock to bas (low) at 3 o'clock.

  • The TAG Heuer Grand Carrera (Ref. CAV5115.BA0902) has a completely different design. Placed at the 9 o'clock position, there is a simple vertical display for the remaining power reserve, which is not inscribed with words or numbers, but only with dashes. All of these markings are white, except for the bottom line, which indicates in red that the watch should be rewound.

  • The Cartier Tortue (Ref. W1542751 2688G) offers one of the most classic power reserves at the 6 o'clock position. This type of power reserve display is visually reminiscent of a car's tachometer and is one of the most popular ways of visualizing this complication.

  • A classic such as the Jaeger-LeCoultre Reverso Grande Date 8 Day Power Reserve (Ref. Q3008420 240.8.15) already reveals the complication can be found on its dial in the name. The eponymous power reserve indicator is located in the upper left-hand corner between 10 and 11 o'clock.

  • Even the notorious Patek Philippe Nautilus (Ref. 3710/1A-001) knows how to shine with power reserve displays and presents them in this model with fascinating simplicity. On this model, the power reserve indicator is located slightly off-centre at the 59th minute – refreshingly untypical.

TAG Heuer Grand Carrera CAV5115.BA0902 stainless steel watch with vertical power reserve display on a black dial

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