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It began with a flicker rather than a roar. The first commercially available solar-powered watch came from the American inventor Roger W. Riehl in 1972 with the launch of the Synchronar 2100. This wasn’t just a novelty—it was a revolution in micro-engineering. Riehl wasn’t content with fitting solar panels into a traditional watch; he redesigned the case entirely to face the sun optimally, with the LED display mounted vertically for easier reading. It was a vision of the future sculpted in the constraints of 1970s technology. The Synchronar was ahead of its time—perhaps too far ahead—but it laid the philosophical groundwork: a timepiece that was no longer dependent on battery replacements, but fuelled directly by ambient light.
Japan, as it often does in the world of practical horological innovation, saw the potential early and ran with it. Seiko, who had already stunned the Swiss with the Astron quartz in 1969, began experimenting with solar technology not long after. By 1977, the first Seiko solar prototypes appeared, but it wasn’t until the 1980s that commercially viable models began to hit the market. The 1988 Seiko Solar became their mainstream entry, the first wristwatch in the world to use photovoltaic cells under the dial and store energy in a rechargeable cell. It was efficient, reliable, and crucially, affordable.
As quartz movements matured, so too did solar. The challenge Seiko tackled was miniaturisation—reducing the size of the solar cell while improving its sensitivity. They achieved this by embedding multi-layered amorphous silicon cells that could absorb light even in dim indoor conditions.
“Embrace the sun with solar-powered watches, where innovation meets sustainability—enjoy the freedom of never winding again, while harnessing nature’s energy to keep you on time, effortlessly.”
-Kev Green
Citizen, meanwhile, wasn’t content with merely competing—they wanted to own the solar conversation. In 1995, they launched Eco-Drive, a name now synonymous with solar technology. What set Eco-Drive apart was its ability to charge not only in sunlight but also under artificial lighting with remarkable efficiency. The movements featured a titanium lithium-ion battery that could hold a charge for up to six months or more, some models even stretching into multi-year reserves on a full charge. And Citizen didn’t just build watches—they built infrastructure, investing in solar labs and driving forward patents that refined both energy storage and charging sensitivity. Their 2009 Eco-Drive Ring, with solar panels encircling the dial’s perimeter rather than covering its surface, showcased how beautifully the technology could integrate into high design. It was an award-winning concept that challenged the assumption that solar needed to look utilitarian.
Both Seiko and Citizen began to treat solar not as an alternative, but as a superior solution for everyday watch wearers. The battery replacement argument vanished. The environmental angle entered quietly but firmly. And as concerns about sustainability began to dominate the 21st-century conversation, the groundwork had already been laid by these Japanese giants.
Casio, ever the democratic technologist, brought solar to the masses through G-Shock. The Tough Solar system combined solar recharging with shock resistance, atomic timekeeping, and extreme durability, becoming the go-to for everyone from rescue workers to astronauts. Some models were equipped with digital compasses, altimeters, thermometers, and even Bluetooth functionality—all powered by light. Casio didn’t market these watches as solar-powered first; instead, they became part of a wider promise of reliability. A G-Shock didn’t need maintenance. It just worked. That was the selling point—and solar made it possible.
But let’s pause here and ask: why didn’t Swiss or German haute horology adopt solar technology more enthusiastically? In short, it didn’t align with their philosophy. Luxury mechanical watches are about the celebration of craft, heritage, and mechanical ingenuity. Solar, despite its marvels, is largely invisible. You can’t see it working. You don’t admire the glide of an escapement or the resonance of a tourbillon in a solar cell. That said, there have been exceptions. Junghans, a German brand with Bauhaus leanings, introduced solar models such as the Force Mega Solar. These combine clean, minimalist design with atomic accuracy and solar recharging. TAG Heuer’s experiment with solar, the Aquaracer Solargraph, debuted recently with sunlight-charging capabilities via a calibre built in partnership with La Joux-Perret. It’s rugged, modern, and subtle—perhaps a sign that even luxury brands now see solar’s role in the evolving landscape.
Miniaturisation remains one of the solar watch’s greatest achievements. Early solar cells were large, crude, and aesthetically dominant. Today, cells can be hidden behind translucent dials, recessed into chapter rings, or embedded in layers no thicker than a sheet of paper. Advances in photovoltaic chemistry and the integration of multi-directional light capture mean that solar watches now charge efficiently even in weak or indirect light. Seiko’s calibre V198, for example, powers an entire solar GMT chronograph with impressive reserve, and Citizen’s newer Eco-Drive movements boast power-saving sleep modes that reactivate with the flick of a wrist.
The patent landscape has been busy, too. Seiko and Citizen hold numerous proprietary methods for light conversion, storage regulation, and dial transparency. One of Citizen’s standout patents relates to a light-level detection sensor that adjusts charge absorption based on available light, extending battery life and reducing energy waste. Other patents focus on multi-source charging, allowing a watch to draw energy from several angles at once. These are not gimmicks—they’re deep technical solutions to challenges faced only at the intersection of physics and design.
Even hybrid solar watches have now emerged. These combine Bluetooth connectivity, fitness tracking, GPS synchronisation, and smart notifications—all fuelled by solar. Garmin’s Instinct Solar and Fenix 7 Solar are excellent examples, allowing weeks of operation without recharging. They redefine what a “connected” watch can be, with solar as the enabling force rather than an afterthought. This hybridisation has ushered solar into a new realm—not just as an alternative to battery or mechanical power, but as the key to independence from power sources entirely.
In a nutshell, the invention of solar provides the following as just a few benefits.
- Eco-Friendly Power Source: Solar watches use sunlight or artificial light to charge their batteries, making them an environmentally friendly option compared to traditional battery-powered watches.
- Low Maintenance: With their solar technology, these watches typically require less maintenance since they don’t need regular battery replacements, which can be both convenient and cost-effective.
- Long Battery Life: Solar watches can store energy for extended periods, often lasting several months on a full charge, ensuring reliable timekeeping even without direct light exposure.
- Durability and Features: Many solar watches are designed to be durable and come with various features such as water resistance, alarms, and chronographs, making them suitable for various activities and lifestyles.
The last barrier is perception
Mechanical watches are still held up as the pinnacle of horological artistry. But for everyday utility, solar has quietly become the most advanced and low-maintenance movement class in the world. It can be accurate to ±15 seconds a month. It can function for six months or more on a single charge. It can survive a beating, sync to atomic time, cross time zones automatically, and still look every bit a proper wristwatch. In many ways, it’s what the quartz revolution promised, finally refined to its logical, elegant conclusion.
And now, in a world increasingly aware of its footprint, the silent energy drawn from light may finally receive its due. Solar watches represent the convergence of utility and responsibility. They ask nothing from the wearer but daylight. They serve without fuss, without ego, without cost to the earth. And in that quiet promise, they become something more than tools. They become timekeepers in harmony with nature itself.
Because in the end, a solar watch doesn’t just measure time. It lives with it. It drinks from the same light that paints your morning and fades your dusk. And there is something undeniably poetic about that.
To read about Citizen’s Eco-Drive, click on the orange arrow.
