Power Reserve in Seiko and NH Movements: Understanding and Improving Your Watch’s Stamina

Power reserve is often considered the ‘stamina’ of a watch, dictating how long it can run without winding. Given the increasing popularity of modding, it’s beneficial to understand how different movements—such as the Seiko 7S26 and NH34, NH35, NH36, and NH38—fare in terms of power reserve and what steps can be taken to improve and measure it.

What is Power Reserve?

Power reserve is the duration for which a fully wound watch can run before stopping. It’s a function of the mainspring’s capacity and how efficiently the movement utilizes that stored energy.

  • Seiko 7S26: Approx. 41 hours
  • NH34: Approx. 45 hours
  • NH35: Approx. 41 hours
  • NH36: Approx. 41 hours
  • NH38: Approx. 41 hours

Measuring Power Reserve

Measuring your watch’s power reserve is a simple process:

  1. Fully Wind the Watch: Either manually or through normal wear.
  2. Set the Time: Preferably to an easily memorable setting like 12:00.
  3. Let it Run: Keep the watch stationary and monitor how long it takes for it to stop.

Improving Power Reserve

  1. Regular Servicing: Cleaning, oiling, and adjusting the movement can optimize power reserve.
  2. Upgrade Mainspring: Consider installing a high-capacity mainspring.
  3. Efficient Gear Train: Modders can sometimes replace gear train components for more efficient energy transmission, although this is an very advanced modification.

Opportunities for Modders

For those who engage in the art of modding, understanding power reserve opens up exciting opportunities for customization. From choosing a mainspring with higher capacity to focusing on movements known for their longevity, modding can enhance a watch’s power reserve, making your custom creation not just aesthetically pleasing but also mechanically superior.


Understanding your watch’s power reserve can enhance your experience as both a wearer and a modder. Whether you’re dealing with a Seiko 7S26 or one of the NH movements, knowledge is power—or, in this case, power reserve.

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