High-quality mechanical watches are not only characterized by their high precision and sophisticated design, but also by technical innovations such as a particularly long power reserve. The power reserve determines how long a watch will run without being wound, before the energy stored in the mainspring is used up. While for standard watches that is often 40 to 50 hours, top models from renowned brands use innovative technology to achieve running times of several days or even a whole month. Many models are equipped with a power reserve indicator that provides information on when the watch needs to be supplied with fresh energy.
How does a mechanical movement work and what is the power reserve?
The functioning of purely mechanical calibers is based on numerous components that interlock precisely. An important part of the mechanism is the mainspring, a spiral-shaped metal spring that serves as an energy store. When the movement is wound, the spring is tensioned and releases the stored energy afterwards. This energy is transferred to the escapement via the gear train, where it is released to the escape wheel by the escapement mechanism. This in turn keeps the balance wheel in motion, while a hairspring ensures the balance wheel has a constant frequency. The gear train then transfers the energy to the hands. The term power reserve refers to the period of time that the spring requires until it is completely relaxed after full winding. That duration depends on the spring length and strength as well as the efficiency of the gear train and the frequency of the balance wheel. Longer mainsprings, precise gear trains, and lower balance frequencies contribute to a longer power reserve. In highly sophisticated models, several barrels are used in parallel, resulting in impressively long power reserves. You can also read the detailed article “What is a watch’s power reserve?” by René Herold on the topic. In this article, we present five popular watches that are characterized by their exceptionally high power reserve.
Watches with a high power reserve
1. IWC Portugieser Automatic 42 – seven-day power reserve
This list starts with the Portugieser Automatic 42 model from the Schaffhausen-based watch manufacturer IWC. First released in 2000, the watch is available with either a stainless steel or rose gold case. IWC also offers a range of different dial colors. Common to all variants is a 42.4 mm large and 12.9 mm high case, which houses the IWC in-house caliber 52011. One example is the stainless steel version ref. IW501701. This model has a silver dial and a black alligator leather strap. The caliber 52011 has a power reserve of seven days or 168 hours. That is made possible by a double barrel and the Pellaton winding system with zirconium oxide ceramic components, in which an eccentrically mounted disc forms the center of the rotor instead of a ball bearing or gear wheel. The balance frequency of the 52011 is 28,800 vibrations per hour (A/h). You can see how much energy the mainsprings have left on the power reserve indicator at the 3 o’clock position on the dial. On Chrono24, you can buy a mint model of this IWC Portugieser Automatic 42 for around $12,400. The rose gold model (ref. IW501707) is significantly more expensive at around $24,000. 
2. Panerai Luminor 1950 10 Days GMT – Ten-Day Power Reserve
A power reserve of seven days is impressive, but ten days is even more impressive. Watches from the Luminor 1950 10 Days GMT series by Panerai, a Swiss manufacturer with Italian roots, offer just that. For this list, let’s take a closer look at the PAM 00335 model. As is typical for Panerai, the case is generously proportioned with a diameter of 44 mm. It is made of black ceramic and features Panerai’s characteristic crown guard, which makes the watch appear even more massive. In addition to the case, the dial and the rubber strap are also black, giving the watch a strikingly dark appearance on the wrist. The Panerai in-house movement P.2003 provides a power reserve of 240 hours, with a total of three barrels responsible for the movement’s staying power. The power reserve indicator is located above 6 o’clock. The P.2003 is also characterized by a Glucydur balance wheel that oscillates at 28,800 vibrations per hour. The KIF-Parechoc shock protection system also ensures that the PAM 00335 can withstand even heavy impacts. The Panerai Luminor 1950 10 Days GMT is available in mint condition on Chrono24 for an average of around $9,700.
3. Oris Pro Pilot Caliber 111 – Ten-Day Power Reserve
The Hölstein-based watchmaker Oris also offers timepieces with a power reserve of 10 days. Among them is the Pro Pilot Caliber 111, one of the earlier models in the Pro Pilot collection. The model is available in the dial colors grey (ref. 01 111 7711 4163-Set 8 22 19) and blue (ref. 01 111 7711 4165-Set 8 22 19), each on a three-link stainless steel bracelet. With a case diameter of 44 mm and a height of around 14 mm, the stainless steel watch is designed for rather sturdy wrists. As is typical for the Pro Pilot series, this variant also combines classic pilot’s watch design with contemporary aesthetics. That combination is reflected on the dial with clearly legible Arabic hour indices, a small seconds display at 9 o’clock with integrated date, and a power reserve indicator at 3 o’clock. At the heart of the watch is the eponymous Oris Calibre 111 in-house manual movement. Oris achieves the high power reserve of ten days with a particularly long mainspring and a reduced balance frequency of just 21,600 vibrations per hour (A/h). The price for an excellently preserved Oris Pro Pilot Caliber 111 on Chrono24 is just over $4,100.
4. Hublot Big Bang Meca-10 – Ten-Day Power Reserve
The Swiss luxury watch icon Hublot offers a whole range of ambitious timepieces equipped with the HUB1201 in-house movement in their Big Bang Meca-10 collection. The caliber HUB1201 is an innovative hand-wound movement that – as the name of the collection suggests – has a power reserve of ten days. That high value is achieved with two barrels and a reduced balance frequency of 21,600 vibrations per hour. The movement is elaborately skeletonized, allowing the mechanism, including bridges and gear train, to be viewed through the crystal. The power reserve indicator is located at 6 o’clock and is displayed using a mechanical rack and pinion system. The HUB1201 is used in the Big Bang Meca-10 Unico Titanium ref. 414.NI.1123.RX, among other watches. The 45 mm octagonal case of this model is made of titanium and has the typical Hublot porthole look with visible decorative screws on the bezel. This model can be found unworn for around $18,700.
5. A. Lange & Söhne Lange 31 Ref. 130.025F – 31-day Power Reserve
What can’t you do in 744 hours? That’s equivalent to a 31-day month and the incredible power reserve of the A. Lange & Söhne Lange 31 (ref. 130.025F). This exclusive white gold model from the Glashütte-based luxury watch manufacturer, limited to 100 pieces, is the world’s first mechanical wristwatch to boast such a long power reserve. The case of the 45.9 mm Lange 31 houses the manually wound in-house caliber L034.1. The caliber is a “posttension movement”, which, despite its enormous power reserve, manages with just two barrels. The functional principle of the movement is as ingenious as it is effective. A small auxiliary spring between the particularly long main springs and the gear train provides the necessary energy. The auxiliary spring itself is (re)tensioned via the main springs and in turn transfers its force to the gear train. The balance frequency of the L034.1 is 21,600 vibrations per hour (A/h). The dial design is typical of Lange & Söhne. There is a large date below 10 o’clock, while a small seconds display is located at 6 o’clock. The power reserve indicator dominates the dial between 2 and 4 o’clock. The Lange 31 is rare on online marketplaces and is offered at prices upwards of $90,000.
Our list of popular watches with a high power reserve ends here. What’s your favorite model?
