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What Is The Power Reserve On A Watch?

What Is The Power Reserve On A Watch?

To put it simply, a power reserve is a feature found on an automatic (mechanical) watch that refers to the amount of time the watch will run after it’s fully wound. In other words, it is the available energy stored in a watch's mainspring, and once the power reserve has run out, your watch will stop. The reason for this is that a mechanical timepiece draws the energy it needs to run the cogs of the mechanism and activate the hands from a complex system, which is kept active by winding it up.

A complication known as the “power reserve indicator” also exists to indicate precisely how much life your watch has left in it, similar to a battery or petrol gauge. While certain watches place the power reserve indicator on the back of the watch in order to free up a face already filled with other displays and complications, it most commonly comes in the form of a hand on the face of the watch, displayed on an arc-shaped or circular dial, indicating the energy or power remaining.

This additional mechanical module is super useful to have in everyday life because it gives the wearer a good indication of when it’s time to wear or wind up their watch in order to prevent it from stopping and needing to be reset.

To help you understand how power reserves work, it’s beneficial to have a general idea of automatic watches and their function:

What Is An Automatic Movement Watch?

An automatic watch operates by a self-winding movement which is powered by the motions of the wearer during use, unlike manual watches that require daily hand-winding. 

The Automatic mechanism is driven by a weighted rotor above the main spring that winds the movement as it’s worn, resulting in the watch being self-winding, and therefore “automatic”.

On average, most automatic watches have a power reserve of between 36 and 42 hours, some even 50 or 70 hours, meaning that the watch can run for that duration on a full wind. 

How Much Power Reserve Do You Need?

The longer the power reserve, the more capable the watch i.e. the longer you can leave your watch between wearing or winding - regardless of how much power reserve is left when you leave it. How much power reserve you “need” mainly depends on your watch wearing habits i.e. do you like to rotate your watches? Do you wear your automatic watch every day? 

The Benefits Of Choosing An Automatic Watch

High Power Reserve

Of course the first benefit of opting for an automatic watch is its high power reserve. Some automatic watches can have up to 50 hours of power stored before you need to wind it up again. Depending on the brand you pick, some automatic watches can even store power for up to 10 days, like the incredible Panerai Luminor GMT 10 Days. 

No Hand Winding Necessary

As long as you wear your automatic watch regularly, you’ll never have to manually wind it which makes it very convenient. If you alternate between a number of different watches, or only wear the automatic watch every so often, you might want to consider getting a watch winder - especially if it has a number of complications that will need resetting every time you wear it.  

You can learn all about watch winders and browse our wide collection here

Low Maintenance 

Another benefit of choosing an automatic watch is that they’re generally easy to maintain. As long as you use a soft cloth to wipe your watch every night, you’ll keep it looking as good as new for years to come. With this in mind, you still need to handle it with caution. Like any other watch, avoid showering or bathing with it (even if it’s waterproof). If this happens, the gasket will end up expanding, reducing the watch’s accuracy and overall lifespan.

Exquisite Aesthetics

The stellar craftsmanship and exquisite engineering makes automatic watches easily one of the most aesthetically pleasing watches on the market today. 

Our Top Automatic Watches 

ZENITH Defy Classic 41mm Titanium Automatic Watch - Blue Dial

Powered by the Elite 670 automatic movement, the Defy Classic is presented in a 41mm titanium case with an integrated titanium bracelet, fitted with a blue sunray-patterned dial. Featuring a 50-hour power reserve and scratch-resistant sapphire crystal, this is a solidly-crafted, reliable wrist watch that's a superb all-rounder.

ROLEX Milgauss 40mm Automatic Watch - Black Dial

The Milgauss is an iconic, pioneering anti-magnetic watch designed to withstand high levels of electromagnetism, originally designed for scientists and engineers. Its design is handsomely understated, punctuated with instantly recognisable hallmarks like its stark orange 'lightning bolt' second-hand and the scratch-resistant green sapphire crystal that pleasingly accents the dial beneath it. It also features a handy 48-hour power reserve. 

TUDOR Black Bay 41mm Automatic Watch (Harrods Exclusive) - Green Bezel & Black Dial

When it comes to long-lasting power-reserves, this Tudor Black Bay timepiece smashes all others out the park with an impressive 70-hour power reserve. 

This unique variant of the venerable Tudor Black Bay, produced exclusively for the world-famous Harrods department store, is a novel and handsomely-adorned slice of opulence. The classic combination of black bezel and gold-edged hands and indexes are encircled by a count-up bezel in Harrods' signature shade of green. The watch comes complete with a lightweight fabric strap in addition to its standard steel bracelet.


Shop our extensive range of automatic watches here. 

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Written by Kate, for Watch Obsession.