Solar watches have become one of the most interesting branches of quartz watchmaking. Instead of relying on a conventional disposable battery, a solar watch uses light to generate electricity, stores that energy in a rechargeable cell, and uses it to power the quartz movement.
But “solar movement” is not really one particular type of movement.
There are hundreds of different solar calibres and modules, ranging from simple three-hand movements to sophisticated chronographs, radio-controlled watches, dive watches, perpetual calendars, Bluetooth watches, and multifunction digital watches.
Some are made by major movement manufacturers such as Citizen, Seiko Instruments, MIYOTA, and Ronda. Others are proprietary systems developed by individual watch companies.
This guide is our attempt to make sense of the solar movement landscape.
We will cover the major manufacturers, important solar movement families, proprietary solar technologies, and some of the individual calibres you are most likely to encounter when researching a solar-powered watch.
Table of Contents
Important: This is a living reference rather than a claim that every solar calibre ever produced is included. Manufacturers have produced many discontinued, regional, private-label, and obscure movements over the years. We will continue expanding this guide as new movements and better documentation become available.
Solar Watch Movements at a Glance
The easiest way to understand the market is to separate movement manufacturers from solar technologies.
Manufacturer / System | Solar Technology | Examples | Typical Watches |
|---|---|---|---|
Citizen | Eco-Drive | E168, E365, 8826 and many others | Citizen |
Seiko | Solar | V110, V147, V157, V158, V192, V194, V195, V198 and others | Seiko |
MIYOTA | Solar Quartz | 2070, 2170 | Multiple brands |
Casio | Tough Solar | Proprietary modules | G-Shock, Pro Trek, Edifice, Casio |
Ronda | Solar quartz | Various Ronda solar calibres | Swiss and international brands |
ETA | Swiss quartz / solar-related technology | Selected specialized calibres | Swiss brands |
Other proprietary systems | Brand-specific | Various | Individual brands |
The important point is that not every solar watch uses a movement that is marketed under a separate solar brand name.
For example, Citizen calls its light-powered technology Eco-Drive. Casio calls its system Tough Solar. Seiko generally identifies its watches by the specific calibre number. MIYOTA classifies its light-powered movements as Solar Quartz.
How a Solar Watch Movement Works
A solar watch is fundamentally a quartz watch with a different power-generation and energy-storage system.
A conventional quartz watch normally uses a disposable battery. A solar watch replaces that arrangement with three important components:
- A solar cell
- A rechargeable storage cell
- An electronic quartz movement
Light reaches the solar cell through the dial or another part of the watch. The cell converts that light into electrical energy, which is stored in the rechargeable cell.
The movement then draws electricity from that stored energy.
This means the watch does not have to be sitting in direct sunlight to operate.
Citizen’s Eco-Drive technology, for example, is designed to use both sunlight and artificial light. Citizen says a fully charged Eco-Drive watch can run for more than six months in darkness, although actual specifications vary considerably by calibre.
MIYOTA’s solar system works on the same basic principle. Its documentation describes a solar cell around the dial, electricity generation, storage in a rechargeable battery, and subsequent use of that stored energy to drive the movement.
Casio’s Tough Solar system similarly uses solar panels and an internal rechargeable battery and is designed to extract energy from relatively weak light sources, including fluorescent lighting.
Citizen Eco-Drive Movements
Citizen is arguably the company most closely associated with solar-powered watches.
Citizen introduced its first Eco-Drive technology in 1976 and has spent decades developing light-powered watches across a huge range of designs and complications. Today Eco-Drive is used in everything from inexpensive everyday watches to professional dive watches and highly complicated radio-controlled models.
One important distinction is that Eco-Drive is not a single movement.
It is Citizen’s proprietary light-powered technology.
The actual watch movement is identified by a calibre number.
Citizen E168
The E168 is one of the Citizen Eco-Drive calibres that frequently appears in modern solar watches.
Citizen’s documentation identifies the E168 as a three-hand movement with date display. The manufacturer’s support documentation also provides specific charging, operating, and troubleshooting instructions for the calibre.
The E168 is particularly interesting because it illustrates how Citizen’s movement numbering works: the consumer may see “Eco-Drive” on the dial, while the case back identifies the actual calibre.
E168 characteristics
- Solar-powered quartz
- Three hands
- Date display
- Rechargeable energy storage
- Citizen Eco-Drive technology
- Used in a variety of Citizen watches
- Available in diver’s-watch applications
Citizen provides separate documentation for E168 applications including watches rated for 200-meter and 300-meter diving.
Citizen E365
The E365 represents a very different direction for Citizen.
Citizen developed this light-powered calibre specifically around an exceptionally long running time. The company says the E365 can operate for 365 days on a single full charge.
That makes the E365 particularly interesting when comparing solar movements because it demonstrates that “solar watch” does not automatically mean all solar movements have approximately the same power reserve.
Calibre design, energy storage, power consumption, and watch functions all affect how long a watch can continue operating without additional light.
Citizen Calibre 8826
The 8826 is another noteworthy Eco-Drive movement.
Citizen developed the 8826 for its Eco-Drive One collection and describes it as the world’s thinnest light-powered analogue movement at 1.00 mm thick, based on Citizen’s research as of November 2023.
It is a useful example of another important characteristic of solar movement engineering: reducing thickness.
Solar watches need a solar cell and energy-storage system, so making a light-powered movement extremely thin presents different engineering challenges from producing a conventional quartz movement.
Other Citizen Eco-Drive Calibres
Citizen has produced a very large number of Eco-Drive calibres.
Among the families and individual calibres that solar-watch enthusiasts may encounter are:
- E168
- E365
- 8826
- E67
- H46
- Various E-series calibres
- Various H-series calibres
- Numerous chronograph, perpetual-calendar, radio-controlled, and multifunction calibres
The exact specifications should always be checked against Citizen’s documentation because the features can vary substantially between calibres.
For example, Citizen documentation for the H46 identifies Eco-Drive operation alongside radio control, local time, and perpetual-calendar functionality.
That is why simply saying “this is an Eco-Drive movement” isn’t enough to describe a watch accurately.
Seiko Solar Movements
Seiko takes a somewhat different approach with their Seiko Watches.
Rather than giving its solar technology a consumer-facing name comparable to Eco-Drive, Seiko generally identifies its quartz movements by their calibre numbers.
The manufacturer’s own support database currently lists a large range of solar calibres, including V110, V111, V114, V115, V116, V117, V131, V137, V138, V145, V147, V157, V158, V172, V174, V175, V176, V181, V182, V187, V192, V194, V195, and V198.
This makes the Seiko family particularly interesting for anyone trying to identify the movement inside a particular watch.
Seiko V157
The V157 is one of Seiko’s best-known solar calibres.
Seiko identifies the V157 as a solar calibre and also provides separate documentation for its use in diver’s watches.
The calibre is particularly common in Seiko’s solar dive-watch ecosystem.
That makes the V157 a movement worth knowing if you are researching Seiko solar divers.
Seiko V158
The V158 is another solar calibre with diver’s-watch applications.
Like the V157, Seiko provides separate instructions identifying the calibre both as a solar movement and as a movement used in air-diving watches.
The V157 and V158 are therefore useful examples of why movement numbers matter.
Two watches may both be described simply as “Seiko Solar Diver” while containing different calibres with different specifications.
Seiko V192
The V192 is one of Seiko’s more feature-rich solar analogue movements.
Seiko identifies it specifically as an Analog Quartz Solar calibre and also provides documentation for its use in diver’s watches.
The V192 is particularly associated with chronograph-style watches.
This is a good example of how solar technology has moved beyond simple three-hand watches. A solar movement can power multiple hands, chronograph functions, and additional displays without requiring a conventional disposable battery.
Seiko V194, V195 and V198
The V194, V195, and V198 are additional Seiko analogue solar calibres.
Seiko’s official instruction database identifies each as an Analog Quartz Solar movement.
These calibres are worth including in any serious reference database because they demonstrate the breadth of Seiko’s solar movement portfolio.
Other Seiko Solar Calibres
The Seiko solar family extends considerably beyond the calibres discussed above.
Some of the important numbers to know include:
- V110
- V111
- V114
- V115
- V116
- V117
- V131
- V137
- V138
- V145
- V147
- V14J
- V157
- V158
- V172
- V174
- V175
- V176
- V181
- V182
- V187
- V192
- V194
- V195
- V198
Seiko’s official support database is particularly useful when identifying an unknown calibre because the manufacturer provides manuals indexed by the calibre number.
MIYOTA Solar Quartz Movements
MIYOTA is particularly important because its movements are supplied to watch manufacturers around the world.
MIYOTA describes its solar-powered movements as Solar Quartz.
Its solar technology uses a solar cell around the dial to capture light, converts that light to electricity, and stores the energy in a rechargeable battery.
MIYOTA specifically identifies the 2070 and 2170 as its two representative three-hand Solar Quartz movements. Both are based on the company’s famous 2035 platform.
MIYOTA 2070
The 2070 is a three-hand solar quartz movement.
Its specifications include:
- 13 2/5 lignes
- 5.98 mm movement height
- Three-hand display
- Solar power
- Four-year running time listed in MIYOTA’s movement documentation
The movement is now listed by MIYOTA as discontinued, which is an important distinction when researching watches using older MIYOTA solar movements.
The 2070 is nevertheless historically important because it represents MIYOTA’s early mainstream Solar Quartz offering.
MIYOTA 2170
The 2170 is the larger counterpart to the 2070.
MIYOTA describes the 2070 and 2170 as its representative three-hand Solar Quartz calibres, with the principal difference being their size.
Like the 2070, the 2170 is now listed as discontinued.
This is a good reminder that a movement appearing in a currently available watch does not necessarily mean the movement itself is still in production.
Casio Tough Solar
Casio deserves its own section because its solar watches don’t fit neatly into the traditional mechanical-watch concept of a movement calibre.
Casio uses its proprietary Tough Solar charging system across a large range of digital and analogue-digital watches.
The system converts light into electrical energy and stores it in an internal rechargeable battery. Casio says the system can use light from sources including fluorescent lamps, not just sunlight.
Tough Solar is particularly important because Casio uses solar power to operate watches with much higher electrical demands than a conventional three-hand quartz watch.
These can include:
- Digital displays
- LED illumination
- Alarms
- Stopwatches
- Sensors
- Radio-controlled timekeeping
- Bluetooth
- GPS-related functions
- Compass functions
- Barometers
- Altimeters
- Thermometers
Casio specifically describes Tough Solar as being capable of supplying power for high-load functions such as measurement, radio reception, Bluetooth connectivity, lighting, and alarms.
Tough Solar and G-Shock
Tough Solar is widely associated with G-Shock.
Some G-Shock watches combine solar charging with radio-controlled timekeeping, Bluetooth connectivity, and other advanced functions.
Casio’s technology documentation also describes a specialized Tough Movement for radio-controlled solar analogue watches, incorporating functions such as Multiband 6 reception and automatic hand-position correction.
This is an important distinction:
Tough Solar is the charging technology.
It should not automatically be treated as the name of one specific movement.
Tough Solar and Pro Trek
Casio also uses Tough Solar extensively in its Pro Trek range.
For example, Pro Trek watches can combine Tough Solar with a digital compass, barometer/altimeter, thermometer, radio-controlled timekeeping, and other outdoor functions.
This makes Casio one of the best examples of how solar power can support a watch that requires considerably more energy than a conventional analogue quartz watch.
Ronda Solar Movements
Ronda is another important Swiss movement manufacturer to know when researching solar watches.
Unlike Citizen and Casio, Ronda does not have the same consumer recognition among watch buyers, but its quartz movements appear in watches from numerous brands.
Ronda has produced solar-powered quartz movements in addition to its extensive conventional quartz portfolio.
For Solar-Watches, Ronda deserves particular attention because a watch marketed simply as a Swiss Made solar watch may contain a Ronda movement rather than a Citizen or Seiko calibre.
We should therefore treat Ronda as an important movement manufacturer in its own right rather than assuming that all Swiss solar watches use ETA.
ETA and Swiss Solar Quartz
ETA is another major Swiss movement manufacturer.
The Swiss quartz market is different from the Japanese market, with movement development often emphasizing thinness, compact dimensions, specialized complications, and integration into Swiss watch manufacturing.
One important point when researching Swiss movements is that not every ETA quartz calibre is solar-powered.
For example, ETA’s F06.161 is a conventional quartz movement with a battery rather than a solar movement. ETA lists the calibre as an 11½-ligne movement measuring 25.60 mm in diameter and 3.60 mm thick, with hours, minutes, central seconds, big date, and three jewels.
That distinction matters because movement databases and watch listings sometimes lead readers to assume that a Swiss quartz movement is automatically solar.
It isn’t.
Proprietary Solar Movement Systems
The major movement manufacturers are only part of the story.
Some watch companies develop proprietary solar systems or heavily customize movements supplied by another manufacturer.
This is particularly common in watches with:
- Radio-controlled timekeeping
- Perpetual calendars
- GPS
- Bluetooth
- Multiple time zones
- Chronographs
- High-performance dive functions
- Specialized displays
As a result, the phrase “solar movement” can refer to several different things:
- A complete movement manufactured specifically as a solar calibre
- A quartz movement integrated with a solar charging system
- A proprietary module incorporating solar charging
- A brand-specific technology built around one or more movement families
This is why identifying the actual calibre number is often more useful than simply knowing that a watch is solar-powered.
Solar Technology vs. Solar Movement
These terms are often used interchangeably, but they are not identical.
Solar technology
This describes the system that generates and stores electrical energy from light.
Examples include:
- Citizen Eco-Drive
- Casio Tough Solar
- MIYOTA Solar Technology
- Seiko Solar
Solar movement
This describes the actual calibre or module being powered by that system.
Examples include:
- Citizen E168
- Citizen E365
- Citizen 8826
- Seiko V157
- Seiko V192
- MIYOTA 2070
- MIYOTA 2170
The distinction becomes especially important when comparing watches.
Two watches can both use solar power while having completely different movements, energy storage, accuracy, complications, and service requirements.
Why the Movement Matters When Buying a Solar Watch
A solar watch is not automatically a good solar watch.
The movement determines much of the watch’s real-world performance.
When comparing two solar watches, we recommend looking at at least these factors.
1. Accuracy
Quartz movements are generally very accurate, but specifications vary.
Don’t assume that all solar quartz movements have identical accuracy simply because they use the same basic technology.
2. Power Reserve
This is one of the most important specifications.
A solar watch with a six-month reserve is very different from one designed to run for a year or more in darkness.
Citizen’s E365 is an excellent example of how far manufacturers can push this characteristic, with Citizen specifying 365 days of operation from a full charge.
3. Charging Requirements
Some solar movements are extremely easy to keep charged under ordinary indoor lighting.
Others benefit from regular exposure to stronger light.
MIYOTA explicitly states that its Solar Technology can use sunlight as well as dim indoor light, while Casio similarly designs Tough Solar to work with relatively weak light sources.
4. Functions
A simple three-hand movement consumes much less energy than a watch equipped with:
- Chronograph
- Alarm
- Radio reception
- Bluetooth
- GPS
- Illuminated display
- Sensors
- Perpetual calendar
This is one reason solar watches with advanced electronics can have substantially different power-management requirements.
5. Size and Thickness
Movement dimensions matter when designing or buying a watch.
A large movement may require a larger case.
A thin movement can make a much slimmer watch possible.
Citizen’s 8826 demonstrates how far this engineering can be pushed: Citizen developed it as an extremely thin light-powered analogue movement at just 1.00 mm.
Solar Quartz vs. Conventional Quartz
Solar quartz is still quartz.
That point is worth emphasizing.
A solar watch does not replace the quartz oscillator with some fundamentally different timekeeping mechanism.
Instead, the major difference is where the electrical energy comes from.
A conventional quartz watch:
Disposable battery → quartz movement
A solar quartz watch:
Light → solar cell → rechargeable storage cell → quartz movement
The timekeeping principle remains quartz-based.
The power-generation and storage system is what changes.
Do Solar Watches Have Batteries?
Technically, the terminology can be confusing.
Solar watches generally use a rechargeable energy-storage cell, rather than a conventional disposable quartz-watch battery.
Manufacturers use different terminology for these components, including rechargeable battery, secondary battery, storage cell, or energy-storage cell.
MIYOTA’s 2070 parts documentation, for example, specifically lists a secondary battery as part of the movement.
The important practical point is that the energy-storage component is rechargeable and is replenished by the solar cell.
That does not mean it will last forever.
Rechargeable cells can eventually deteriorate and may require replacement during the service life of the watch.
Which Solar Movement Is the Best?
There is no single answer.
The best solar movement depends on what you want the watch to do.
Best-known light-powered technology
Citizen Eco-Drive
Citizen has an exceptionally long history with light-powered analogue watches, dating back to 1976.
Best for rugged multifunction watches
Casio Tough Solar
Tough Solar is particularly impressive when combined with G-Shock and Pro Trek watches because the system can support numerous power-hungry functions.
Best-known Japanese analogue alternative
Seiko Solar
Seiko offers a large range of solar calibres, from relatively simple watches to chronographs and dive watches.
Important third-party movement supplier
MIYOTA
MIYOTA is particularly important when you encounter a solar watch from a brand that does not manufacture its own movements. Its Solar Quartz range demonstrates that solar technology is not limited to Citizen, Seiko, and Casio.
Solar Movement Manufacturers Worth Knowing
As we expand this database, these are the manufacturers and systems we consider particularly important.
Citizen
Technology: Eco-Drive
Important calibres: E168, E365, 8826, E67, H46 and many others.
Citizen is one of the pioneers of modern light-powered watches and remains one of the largest manufacturers of solar movements and watches.
Seiko
Technology: Solar
Important calibres: V110, V137, V145, V147, V157, V158, V172, V175, V192, V194, V195, V198 and others.
Seiko’s official documentation confirms a large and diverse solar calibre family.
MIYOTA
Technology: Solar Quartz
Important calibres: 2070, 2170 and additional developments.
MIYOTA is particularly significant because its movements are supplied to other watch manufacturers.
Casio
Technology: Tough Solar
Movement/module structure: Proprietary Casio modules and systems.
Casio’s approach is particularly different because solar charging is frequently integrated into highly electronic digital and analogue-digital watches.
Ronda
Technology: Solar quartz
Role: Swiss movement manufacturer and supplier.
Ronda is an important name to know when researching Swiss Made solar watches.
ETA
Technology: Primarily known for Swiss quartz and mechanical movements, with solar-related applications in the broader Swiss movement ecosystem.
ETA should be researched calibre-by-calibre rather than assuming that every ETA quartz movement is solar.
How to Identify the Movement in a Solar Watch
The easiest place to start is the case back.
Many manufacturers engrave the calibre number on the rear of the watch.
For Seiko, the manufacturer specifically tells owners to check the case back to find the calibre code and then use that code to locate the appropriate instruction manual.
For Citizen, the movement number can similarly be used to locate the manufacturer’s documentation.
Once you know the calibre number, you can usually determine:
- Movement manufacturer
- Movement type
- Functions
- Charging characteristics
- Power reserve
- Operating instructions
- Service information
- Replacement parts
- Compatible watches
This is far more reliable than trying to identify a movement from photographs alone.
Solar Movement Reference Table
Here is the core reference list we will continue expanding.
Manufacturer | Calibre / System | Type | Status / Notes |
|---|---|---|---|
Citizen | E168 | Eco-Drive quartz | Widely used |
Citizen | E365 | Eco-Drive quartz | 365-day running-time design |
Citizen | 8826 | Eco-Drive quartz | Ultra-thin |
Citizen | E67 | Eco-Drive quartz | Multifunction examples |
Citizen | H46 | Eco-Drive quartz | Radio-controlled / perpetual-calendar applications |
Seiko | V110 | Solar quartz | Solar analogue |
Seiko | V137 | Solar quartz | Solar analogue |
Seiko | V145 | Solar quartz | Solar / diver applications |
Seiko | V147 | Solar quartz | Solar / diver applications |
Seiko | V157 | Solar quartz | Solar / diver applications |
Seiko | V158 | Solar quartz | Solar / diver applications |
Seiko | V172 | Solar quartz | Solar analogue |
Seiko | V175 | Solar quartz | Solar diver applications |
Seiko | V192 | Solar quartz | Chronograph / diver applications |
Seiko | V194 | Solar quartz | Analogue solar |
Seiko | V195 | Solar quartz | Analogue solar |
Seiko | V198 | Solar quartz | Analogue solar |
MIYOTA | 2070 | Solar Quartz | Discontinued |
MIYOTA | 2170 | Solar Quartz | Discontinued |
Casio | Tough Solar | Proprietary system | Digital / analogue-digital |
Ronda | Solar families | Solar quartz | Swiss |
ETA | Selected solar applications | Quartz / solar | Calibre-specific |
This table should be considered a starting point rather than the finished database.
The Future of Solar Watch Movements
Solar watch technology continues to evolve in several directions.
The obvious goal is greater efficiency, but manufacturers are also working on:
- Longer power reserves
- Smaller movements
- Thinner movements
- Better performance under indoor light
- More efficient solar cells
- Higher-power electronics
- More sophisticated complications
- GPS and Bluetooth integration
- Improved energy management
Citizen’s E365 demonstrates the push toward dramatically longer running times, while Casio’s Tough Solar system demonstrates the challenge of powering increasingly sophisticated electronic watches.
The result is that solar watches are no longer limited to simple three-hand quartz watches.
Frequently Asked Questions
What is the most common solar watch movement?
There is no reliable single answer because movement popularity varies by manufacturer and market. Citizen Eco-Drive and Seiko Solar are among the most prominent solar watch ecosystems, while Casio Tough Solar dominates a large segment of digital and multifunction watches.
Is Eco-Drive a movement?
No.
Eco-Drive is Citizen’s proprietary light-powered technology. Individual Citizen watches use specific Eco-Drive calibres such as E168, E365, and 8826.
Is Tough Solar a movement?
Not in the traditional sense.
Tough Solar is Casio’s proprietary solar charging system. Casio integrates it into different watch modules and electronic systems.
Are Seiko Solar watches quartz?
Yes. Seiko identifies its solar calibres as analogue quartz solar movements in its official documentation.
Are MIYOTA solar movements still made?
MIYOTA’s solar portfolio has changed over time. The company currently lists the 2070 and 2170 as discontinued, so older watches containing those movements should not be assumed to use a currently manufactured calibre.
Do solar watches work without sunlight?
Yes.
Solar watches can operate using stored energy, and many are designed to charge from artificial indoor lighting as well as sunlight. Citizen, MIYOTA, and Casio all document operation using sources beyond direct sunlight.
How long does a solar watch run in darkness?
It depends entirely on the calibre.
Some movements can run for months, while specialized movements can run substantially longer. Citizen’s E365, for example, is designed for 365 days of operation from a full charge.
Do solar watch batteries eventually need replacing?
The rechargeable energy-storage component can eventually degrade and may require service or replacement. “Solar” does not mean that every component of the watch lasts forever.
Our Solar Movement Database
This page is intended to become a living reference for solar watch movements.
As we research individual calibres, we will add them to this database along with:
- Manufacturer
- Calibre number
- Movement type
- Dimensions
- Functions
- Accuracy
- Power reserve
- Charging characteristics
- Rechargeable-cell information
- Production status
- Watches that use the movement
- Manufacturer documentation
- Related movement calibres
The goal is simple:
If you find a solar watch and want to know what is inside it, this should be one of the first places you check.
And just as our All Solar Watch Brands reference helps answer who makes the watch, this guide is designed to answer the other important question:
What powers it?
