Solar watches are an eco-friendly alternative to traditional quartz watches with lithium battery-powered movements, and solar watches still maintain the accuracy and reliability of quartz technology, which makes them much more precise than any mechanical watch. Here's a brief history of solar technology in watchmaking and a selection of notable solar watches on sale now.
Solar Watch Technology - A Brief History
In the late 1960s, the Swiss watch industry was on the precipice of a technical revolution that would ultimately threaten the very existence of traditional mechanical watchmaking while simultaneously ushering in the dawn of mass-produced electronic watches. By the 1970s, quartz movements had won out over a handful of other early technological approaches to producing electronic watches (you can delve a bit more into that history here), giving rise to the era now known known within the industry as the Quartz Crisis. Experiments with using solar power to charge watches, however, go all the way back to the '60s, to the development of the first solar-powered movement by American engineer Roger Riehl. This technology was introduced to the market in 1972, with the first prototype called the “Synchronar” and the first production piece, the Synchronar 2100, released later that same year.
Priced at nearly $500 (about $3,200 in today's money), the Synchronar 2100 was considered something of a luxury product and struggled to compete in the market against the cheaper, more accessible quartz-powered watches that continued to proliferate. Nevertheless, the model set the stage for brands such as Citizen, which would utilize solar technology in watch movements when its costs decreased and production capacity increased. Today, Citizen’s Eco-Drive technology, introduced to the market in 1976, is dominant in the still relatively niche arena of solar-powered watches and is perhaps the Japanese company’s most important contribution to the industry. However, Citizen isn’t the only watch company that has developed solar technologies for watchmaking, and not all solar-powered watches are mass-market consumer products. Other brands including Tissot, Seiko, Casio, and Cartier, among others, continue to harness solar technologies within their product lines.
How Solar Watches Work
As the name suggests, solar watches capture, store, and convert light energy into electrical energy. Early solar-powered models had fully exposed solar cells that faced the sun, either on the dial or on top of the case. The Synchronar 2100 went with the latter option and placed the solar cells on top of the case, giving the watch a futuristic look. Today, a solar cell is placed just under the dial to achieve the same results. As light is captured by the solar cell and converted into electrical energy, it’s then relayed to a rechargeable battery where it's stored. Despite their name, solar cells can collect light not only from the sun, but also from artificial light sources, albeit at a slower rate.
Advantages of Solar Power
Solar power offers several technical advantages over both traditional mechanical movements and modern quartz movements, making it an appealing option for many. First and foremost, the energy to run the movement comes from the ultimate energy source, the sun, which will be abundant for at least another billion years or so, offering plenty of light energy to capture and convert. Secondly, the storage of energy in solar watches, in the context of power reserve, far exceeds anything any mechanical watch can achieve; it's also a feature that's completely absent in traditional battery-operated timekeepers. Thirdly, required maintenance intervals for solar watches are few and far between. Since solar-powered movements require neither lubrication nor a standard battery, it could be a decade of longer before they need servicing. Finally, solar powered movements are at least as accurate as their battery-operated counterparts, utilizing a quartz crystal to power the gear train at extremely high frequencies, thus making these watches accurate within just seconds per month. The low cost of ownership, relatively inexpensive price point, and high level of accuracy make solar technology a legitimate third option among the mechanical and battery-powered timepieces.
Solar Watch Options
Below is a curated list of some solar-powered options across different price points from the iconic Casio G-Shock Full Metal 5000 to the luxurious Cartier Tank Must SolarBeat.
Tissot T-Touch Connect Solar
Tissot brings together both solar and smartwatch technologies with the T-Touch Connect Solar. It’s an impressive piece with an equally impressive size, coming in at 47mm in a hypoallergenic titanium case. It connects to your mobile device with Tissot’s proprietary app, syncing messages, calls, and alerts while also providing health monitoring functions. True to its name, the T-Touch has a tactile crystal that allows the wearer to select functions by touching the large, interactive screen. Yes, the watch's sheer size might limit its audience to those with larger wrists, but the added smartwatch functionality might well appeal to another segment of buyers, outside of the watch enthusiast community, for whom case size is secondary to the tech.
Case: 47.5mm, Thickness 15.3mm, Lug-to-Lug: 60mm, Crystal: Tactile Sapphire, Movement: Solar Quartz E32.001, Water-Resistance: 100m, Price: Starting at $1,050 on the rubber strap
Seiko Prospex SNE435
Speaking of size, another benefit of a solar-powered movement that is often overlooked is its relative thinness, which in turn allows for a thinner case. In the dive watch category, where case thickness can be prohibitive for some, Seiko uses such a movement in the SNE435 model from its sporty Prospex line. While it’s not exactly small in its diameter (43.5mm), its profile is less than 12mm thick, a direct and welcome byproduct of the thinner solar movement inside. In classic Seiko style, the SNE435 boasts high levels of finishing throughout the case and bracelet and sports some of the best luminous dial elements in the industry thanks to the Japanese watchmaker's proprietary LumiBrite material..
Case: 43.5mm, Thickness 11.6mm, Lug-to-Lug: 50mm, Lug Width: 20mm, Crystal: Hardlex, Movement: Solar Quartz V157, Water-Resistance: 200m, Price: $395
Casio G-Shock Full Metal 5000
A favorite among military service personnel, firefighters, and police, the G-Shock embodies extreme durability and reliability with its iconic design. Many models start at under $100, and if you’re willing to spend around $500, you can acquire some of the higher-end models such as the solar-powered G-Shock Full Metal 5000. Like the Tissot T-Touch, the Full Metal 5000 combines solar power with smartwatch technology, synching the time with your cellular device and keeping dead-on accuracy. Pairing all this technology with one of the most robust case designs in the world, Casio has created a timepiece that sets the standard for an everyday wearer.
Case: 49.3mm x 43.2mm, Thickness 13mm, Crystal: Hardlex, Movement: Solar Quartz Module 3459, Water-Resistance: 200m, Price: $550 on the bracelet
Seiko "Arnie" SNJ025
Based on the Seiko reference H558-5000, a watch that Hollywood action star Arnold Schwarzenegger wore in the 1980s blockbusters Commando and Predator, the SNJ025 was launched in 2019, retaining the "tuna can"-style case concept and analog-digital display of the original while also upgrading the watch with a modern solar quartz caliber that addressed the one weakness of its screen-worn predecessor, namely its occasional poor battery life. Size-wise, the SNJ025 is a watch made for a Mr Olympia, even larger than the original watch, which measured just under 46mm. It's also a true ISO-certified dive watch with 200 meters of water resistance and an impressively luminous dial, as one has come to expect from Seiko.
Case Size: 47.8mm; Thickness: 13.8mm; Lug-to-Lug: 50.5mm; Lug Width: 22mm; Water Resistance: 200m; Movement: Seiko Quartz H851; Crystal: Hardlex; Price: $525
Citizen Eco-Drive Promaster Nighthawk
The current-generation Citizen Promaster Nighthawk is a refreshed military-inspired aviation watch that goes big on the functionality and bold on the design. The sporty 42mm case features a slide-rule bezel to go along with the dual time zone, chronograph, and date. Well-suited for use in the sky, its 200 meters of water resistance means it has some underwater abilities, too. Powered by Eco-Drive, the Nighthawk will be ready when you are, whether it's your daily wearer, your weekend go-to, or something you throw on just once in a while. Two color options are available, one in steel with a sunburst charcoal dial on the olive drab strap as well as on all-black version.
Case Size: 42 mm, Thickness: 12.5 mm, Lug-to-Lug: 46.5 mm, Water Resistance: 200 m, Movement: Eco-Drive, Crystal: Sapphire, Price: $495
Citizen Eco-Drive Garrison
Solar technology isn’t limited to any particular style of watch, although it’s most closely associated with sportier, multi-function timepieces. However, with the Citizen Eco-Drive Garrison, you get the benefits of the quartz accuracy, the six-month power reserve, and low-cost technology packaged in a casual, military-inspired field watch with a stylish everyday versatility. The Garrison offers a no-nonsense approach to displaying time, with large, bold Arabic numerals loaded with lume and hands that complement the dial design well. At 42mm, it’s a bit larger than some popular mechanical field watches from Hamilton and Bulova, but the Garrison comes in at less than half the price of both.
Case Size: 42 mm, Water Resistance: 100 m, Movement: Eco-Drive E111, Crystal: Mineral, Price: $200
Citizen Promaster Diver Eco-Drive
Perhaps the most important technological advantage of solar-powered watches is their ability to perform when called upon — no winding or setting required and no unexpected dead batteries. This is why the Citizen Promaster Diver is a widely regarded choice among professional divers who don’t necessarily see themselves as “watch people,” but rely on their watch as yet another piece of high-performance equipment to keep them safe. The Eco-Drive version of the Promaster Diver is one of those tool watches that makes good sense, with its six-month power reserve and decade-long service intervals. In addition to the technology packed inside, its external features include bold, easily legible hands and markers along with a rock-solid ratcheting bezel.
Case Size: 44mm, Thickness: 12mm, Lug-to-Lug: 49 mm, Lug Width: 20mm, Water Resistance: 200 m, Movement: Eco-Drive E168, Crystal: Sapphire, Price: $221.50
Cartier Tank Must SolarBeat
Cartier's introduction of the Tank Must SolarBeat in 2021 was an intriguing move by one of the world’s most important luxury brands. Not only has ultra-traditional, ultra-fashionable Cartier boldly embraced solar technology but it has decided to utilize it in its most iconic watch collection, the Tank. In many ways, this move into solar and away from traditional battery-powered movements, makes a lot of sense, particularly in a women’s model. Solar has proven itself to be one of the best set-it-and-forget-it options available. Of course, the Cartier Tank Must SolarBeat is a step up in price relative to the other options on this list, but within the luxury market, the $2,600 price point fits well within the Cartier catalog, at least in comparison with the brand's quartz-powered Tank models.
Case Size: 33mm x 25.5mm and 29.5mm x 22mm, Thickness: 6.6mm, Water Resistance: 30 m, Movement: SolarBeat, Crystal: Sapphire, Price: $2610
Junghans Max Bill MEGA Solar Titanium
The only German watch brand represented on this list, Jughans traces its history all the way back to 1841 and is today well known for its minimalist, heavily Bauhaus-inspired designs. Fittingly, the brand’s flagship collection is named for Max Bill, the Swiss architect and industrial designer who helped popularize the Bauhaus style. Junghans uses a variety of movements in the Max Bill collection, including the solar-powered quartz caliber that powers the MEGA Solar Titanium model, with a 38mm case made of titanium. Solar charging is made possible by the construction of the matte gray dial, and in another high-tech plus that you generally won’t find in similar watches in this streamlined, “form-follows-function” style, setting the time and date can be accomplished easily via a radio-controlled time signal from an accompanying Junghans MEGA app.
Case: 38mm, Thickness 9mm, Lug-to-Lug: 42.5mm, Lug width: 20mm, Crystal: Convex hard plexiglas, Movement: Connected radio-controlled solar movement J101.85, Case material: Titanium, Price: $1,050
Casio Edifice Solar Chronograph
These days, we mostly think of G-Shock when we think at all about Casio’s most high-tech, sporty and functional watches, but Casio’s Edifice collection, stylishly analog and motorsport-inspired in their design, deserve more attention, both for their array of functions as well as their value prospect. For under $200, you can acquire this steel-cased, chronograph-equipped timepiece with an eye-catching carbon fiber dial with cleverly cut-out subdials to allow light to penetrate a tiny solar panel and the battery behind it. The stainless steel case has a black IP-coated bezel and a 100-meter water resistance and fastens to the wrist with an integrated steel link bracelet. In addition to the elapsed chronograph minutes and seconds, the dial displays the 24-hour time, the date, and an indicator for the battery life, in addition to a reading ot the time that’s accurate to +/- 20 seconds per month.
Case: 47.5mm, Thickness: 12.7mm, Lug-to-Lug: 50mm, Crystal: Mineral glass, Movement: Solar-powered Quartz, Water resistance: 100 meters, Price: $165