Power Sources

The most commonly recognisable type of watch energy supply (and the most traditional) is the spring power supply. This is a very simple mechanism that features a wound spring that functions as a power supply; the major drawback to using this method is that once a day (or even less depending on the timepiece) the spring needs to be wound up again by the watch owner. This is the historic de facto standard and power supply that most people recognise as being traditional to watches .

The first self winding mechanism was invented in 1770 and since has become a staple of horological construction; a self winding power supply refers to any watch that will wind up its own spring by any means other than the actual watch owner physically winding it. The most common method of utilising a self winding energy supply is by using a weight (known as a winding rotor) that is connected to a ratchet that will move backwards and forwards to re-wind the spring as the movement of the wearer's body makes the winding rotor move.

The kinetic power supply traces its routes back to the aforementioned self winding mechanisms however more often they use the movement of the wearer of the watch to power a generator which supplies power to an electronic movement of some sort. The only real difference between the kinetic power supply and the self winding power supply is that the former generates electrical power, the latter mechanical power.

By far the most common power supply for modern watches is the humble battery. The vast majority of watches that use a battery as their main power supply use a replaceable type that allows the user to replace it when it runs down and no longer provides enough charge to power the timepiece. Most batteries used in watch construction will provide continuous power and keep a watch accurate for over two years, some as long as five years. In some cases the watch owner will not be able to replace the battery themselves and a trip to a watch-maker is required as the process can sometimes be delicate or the water-proof seal can sometimes be broken and not replaced if the watch is not serviced by someone experienced in horology .

One of the most modern forms of energy supply for watches is light (or solar) power. A photovoltaic cell is usually located on the dial of the timepiece that will convert visible light into electrical power which will either charge a rechargeable battery or a capacitor to supply movement. This battery or capacitor then powers the movement of the watch, and many watch manufacturers advertise that if the watch is exposed to enough sunlight it will never need a battery replacement, although occasionally (after a very long time, ten years or more) the battery will loose its ability to hold a charge and will have to be replaced. Some of the more expensive types of solar energy supply watches only require a few minutes of light per day to produce a full charge that will last for many weeks. The ecological benefits of watches that feature a solar power supply are what attract a lot of customers; although modern lithium ion batteries can supply over ten years of energy a solar powered watch should theoretically never need to be replaced so there is no waste and a very low input of energy.