A Quick Guide To The Power Reserve Indicator

Welcome to Horology in a Hurry, a semi-regular column in which we'll break down these terms at length one at a time to give you a better understanding of how watches work A simple albeit incredibly useful complication, the power reserve indicator essentially lets the wearer know how much tension is left in a mechanical watch's mainspring in the form of a small hand and a correlating scale given in hours Early marine chronometers and railroad-grade pocket watches featured power reserve indicators, though the first wristwatches with this complication didn't come into being until the 20th century.

While a fully-wound mechanical watch will often feature a power reserve of up to two days, it can be useful to know for precisely how many more hours the watch will continue to function until it will require another winding - otherwise, you may find yourself looking down at a watch that has quite suddenly ceased to tell you anything useful or relevant As the length of the mainspring correlates directly with the amount of power reserve in the watch, many high-end watches utilizing longer main springs have power reserves of several days JLC makes some of the most elegant complicated watches in Swiss Watchdom, so it should be no surprise that they can execute a graceful power reserve complication without cluttering a dial.

The automatic-winding Reserve de Marche features a 43-hour power reserve, and a simple indicator with a blued steel hand in the left-hand sector of the dial lets you know how much of that reserve is left in the mainspring. . Source