The Garmin Instinct 3 Solar is the cheapest watch here and the battery champion, but only because it strips away almost everything. The Amazfit T-Rex Dual Solar is much more of a modern watch, with a bright AMOLED touchscreen and offline maps, but it costs nearly twice as much and cannot come close to the Instinct’s ability to go on almost forever. These are two watches answering the brief for a rugged watch in totally different ways.
You’re probably here for battery life, though. That is the Instinct’s whole argument, so it is worth understanding what you need to lose to save money.
Two watches, opposite priorities
One watch stays minimal to go the distance. The other packs in hardware and leans on solar for long adventures.
- The Instinct is built around battery life first. Garmin gives it a basic monochrome screen, no touch and no maps, then turns those low demands into battery figures the Amazfit cannot match.
- The Amazfit is built around a great display and features first, with maps and a touchscreen, then adds two solar panels to claw back some of the energy those features cost.
Why the Instinct’s battery is unlimited, and the Amazfit’s is not
The Instinct 3 Solar uses a monochrome MIP transflective display at 176x176px, controlled by buttons. It is dim and basic, but it uses so little power that a small Power Glass solar ring can keep pace with the drain. Garmin claims the 45mm can run with unlimited battery in smartwatch mode given about three hours a day of sun at 50,000 lux.
The Amazfit keeps a bright 1.32-inch AMOLED at 466 x 466 and a super bright 3,000 nits. It looks far better, but that screen draws much more power, so its front solar ring does much less for it, lifting typical use from 25 to 34 days; Amazfit also added a larger rear panel that charges only when the watch is off your wrist. The screen’s power draw matters as much as the solar hardware in determining how far solar goes.
Specifications compared
The figures below are for the 45mm Instinct 3 Solar, the cheapest and most direct rival. The 50mm is larger, heavier and lasts longer.
| Specification | Amazfit T-Rex Dual Solar | Garmin Instinct 3 Solar (45mm) |
|---|---|---|
| Display type | AMOLED, 3,000 nits, touchscreen | Monochrome MIP, buttons only |
| Display size and resolution | 1.32 inch, 466 x 466 | 0.9 inch, 176 x 176 |
| Solar | Front ring plus rear caseback panel (rear works off-wrist only) | Front Power Glass ring, works while worn |
| Maps | Offline colour maps | No maps, breadcrumb and course navigation |
| Case | 51.4 x 16.9mm | 45 x 45 x 14.9mm |
| Weight | 69g | 52g |
| Lens and case | Sapphire lens, Grade 5 titanium bezel | Power Glass, polymer case, metal-reinforced bezel |
| Smartwatch battery | Up to 25 days (up to 51 with rear solar, off-wrist) | Up to 28 days (unlimited with solar) |
| GPS battery | GPS accuracy up to 41 hours | Up to 40 hours (up to 130 with solar) |
| Positioning | Dual-band, six satellite systems | Multi-band GNSS, SatIQ |
| Extras | Wi-Fi, mic and speaker, NFC, 64GB, diving to 50m | ANT+, Garmin Pay, no Wi-Fi, mic or speaker |
| Launch price | GBP 649.90 / USD 649.99 | GBP 349.99 / USD 399.99 (50mm from GBP 379.99) |
Battery life
The gap is large and one-sided.
- The 45mm Instinct 3 Solar is rated for up to 28 days in smartwatch mode, or unlimited under Garmin’s solar conditions, and up to 40 GPS hours, rising to 130 with solar. The 50mm lasts up to 40 days, again unlimited with solar, and up to 260 GPS hours with solar.
- The Amazfit lasts up to 25 days, or up to 51 with its rear panel used off the wrist, and up to 41 GPS hours. Amazfit’s 180-day headline applies only to its Outdoor Extreme power-saving mode with continuous rear-panel sun. With GPS running both gain from solar, but the Instinct goes far further with solar, up to 130 GPS hours against the Amazfit’s 57.
What you give up on the Instinct
The battery comes at a cost. The Instinct 3 Solar has no offline maps, only breadcrumb and course navigation, no touchscreen, no Wi-Fi, and no microphone or speaker. Its screen is monochrome and low resolution. The Amazfit has the smartwatch hardware the Instinct lacks: colour maps you can read at a glance, a touchscreen, Wi-Fi, calls through a mic and speaker, 64GB of storage, and recreational diving to 50 metres. Both watches carry the core outdoor sensors, a barometric altimeter and compass, and an LED flashlight, and both have their own training and recovery tools.
The Amazfit also behaves more like a full smartwatch back home and off the trail.
Looks
The Instinct has its own look. Its chunky, polymer, G-Shock-style case is a deliberate rugged aesthetic that many buyers choose for, and others avoid. At 52g in the 45mm size, it is much lighter than the 69g Amazfit. The Amazfit is the more conventional premium watch, with a sapphire lens and a titanium bezel, but it is larger, heavier and has an unusual octagonal case shape. This one is more about style than quality.
Price
The Instinct 3 Solar starts at GBP 349.99 / USD 399.99 for the 45mm and GBP 379.99 / USD 449.99 for the 50mm.
The Amazfit T-Rex Dual Solar is GBP 649.90 / USD 649.99, nearly twice the price of the 45mm Instinct.
The verdict
These are two honest answers to the same question.
- The Instinct 3 Solar wins on battery, price and its distinctive rugged look, but you accept a basic monochrome screen, no maps and few smartwatch features.
- The Amazfit T-Rex Dual Solar wins on screen, maps, features and everyday usability, but costs nearly twice as much, and its solar is mostly a bonus rather than a real battery solution.
If battery life and price come first, buy the Instinct. If you want the nicer screen, maps and a proper smartwatch, buy the Amazfit. The T-Rex Dual Solar hasn’t been tested for accuracy or real-world battery life yet.
Quick answers
Is the Amazfit T-Rex Dual Solar better than the Garmin Instinct 3 Solar?
It depends on what you want. The Amazfit has a far better screen, offline maps and more smartwatch features, but costs nearly twice as much. The Instinct 3 Solar is cheaper, lighter, and lasts far longer on battery, with a basic screen and no maps.
Which has the better battery?
The Garmin, by a wide margin. Garmin claims the Instinct 3 Solar can run with unlimited battery in smartwatch mode given enough sun, because its low-power screen uses very little energy. The Amazfit reaches up to 51 days, and only with its rear panel used off the wrist.
Does the Garmin Instinct 3 Solar have maps?
No. It offers breadcrumb and course navigation but no onboard maps. The Amazfit T-Rex Dual Solar has full offline colour maps.
Why does the Instinct last so much longer?
Its monochrome, low-resolution screen and lack of touch, Wi-Fi, and speaker mean it draws very little power, so a small solar input keeps up. The Amazfit’s bright AMOLED and extra hardware use far more.
Which is cheaper?
The Instinct 3 Solar, at GBP 349.99 for the 45mm, is a little over half the price of the Amazfit at GBP 649.90.
Which should I buy?
For battery life, price and a rugged look, the Instinct. For a bright screen, offline maps and full smartwatch features, the Amazfit.
Full details are on the Amazfit T-Rex Dual Solar specifications and Garmin Instinct 3 Solar specifications pages, in our T-Rex Dual Solar launch coverage, and alongside the pricier Fenix 9 Pro Solar comparison.
Amazfit T-Rex Dual Solar
Solar expedition GPS smartwatch
More: Amazfit coverage, Garmin coverage, and the Release Radar.
Last Updated on 22 September 2026 by tfk the5krunner
Small things I always use
- Garmin 90-degree charging adapter: Charges your Garmin from any USB-C cable. Essential when travelling. I use one.
- Body Glide: The blue anti-chafe stick swimmers and runners carry. I use it.
- Speedo earplugs: Fewer ear infections and no cold-water dizziness. I use them.
- Dryrobe Advance: My winter changing robe for open-water swims. I use one. A cheaper option is the AONYIYI changing robe.
- Maurten: Race fuel that stays easy on the stomach. I use them.
- Beet It Sport nitrate shots: Beetroot shots I take in the days before a race. I use them.
- Garmin charging puck: The quickest way to top up before a session. I use one.
- Injinji: Toe socks that stop rubbing, so you run more. I use them.
- Ultimate toe protectors: Stop black toenails on long runs. They work. I use them.
- Compressport R2 v2 calf sleeves: My calf sleeves of choice. I use them.
- Cellucor C4: My pre-workout before hard sessions.
- TPU tubes: Schwalbe Aerothan, Tubolito and Pirelli SmarTube. Light, tiny spares. I use all three.
- G8 insoles: Adjustable insoles that are good. I use them.
- Cycplus Cube: A 97g electric pump that gets a road tyre rideable in two minutes. I carry one. 5% off with code THE5KRUNNER.
Watches and sensors
- Polar H10: My daily driver for waking HRV.
- Polar Verity Sense: My backup arm-worn HR sensor.
- Nomad bedside charger: Charges my iPhone and Apple Watch overnight. I use it, and many of their bands.
- Train.Red: The best muscle oxygen sensor I’ve used.
- Tymewear: Accurate heart rate and reliable ventilatory zones. I use it to pace endurance rides over an hour.
- Garmin Forerunner 970: A pro-grade triathlon watch. I use this.
- Apple Watch Ultra 4: My daily smartwatch. No phone needed on rides.
- Garmin Fenix 9 Pro: I’ve just bought one.
On the bike
- Continental GP5000 for everyday riding, and Aero 111 on the front for special occasions.
- Helmets: Specialized S-Works Evade 3 for road riding, and Rudy Project Wing for TT-style races. I use both.
- Ravemen FR300: A front light that mounts under your Garmin or Wahoo. I use one.
- Ravemen FR1000: The light and the computer mount in one unit, so nothing else goes on the bars. Better than mine.
- Ravemen FR1500SE: 1,500 lumens hanging under your Garmin, for proper night rides.
- Ravemen FR1100SE: 1,100 lumens under your Garmin, and up to 46 hours on slow flash.
- Ravemen FR500: A brighter FR300 with the same mount.
- Wahoo TRACKR Radar: I use it on one bike and Varia on the other. They perform the same.
- Garmin Varia RTL515: Radar that warns you of cars from behind. I use this model.
- Wahoo ELEMNT Roam 3: The bike computer that’s easy to use. I use mine on most rides.
- Favero Assioma Pro RS2: Accurate power pedals that swap easily between bikes. I use this model.
Home and indoor training
- NPE Runn: Makes my basic treadmill smart, sending more accurate speed and distance to my watch and Zwift. I use it.
- Google Wifi: Keeps Zwift connected in my pain cave. I use it.
- Apple TV 4K: Zwift on the big screen. I use two.
- Google Nest Doorbell (wired, 2nd gen): My video doorbell, running in both Google Home and Apple Home. I use it.
Health, recovery and sleep
- FreeStyle Libre 3 Plus: Shows how my blood sugar responds to diet.
- hDrop: Measures my sweat loss in summer and indoors.
- Fourth Frontier Zone: Checks my heart under load in hard sessions.
- Kineon MOVE+: Red and infrared light for sore knees, Achilles and other joints after hard training. I use it.
- Oura Ring 5: My partner’s recovery tracker of choice.
- Eight Sleep: A cooling mattress cover my partner and I use nightly.
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tfk is the founder and author of the5krunner, an independent endurance sports technology publication. With 20 years of hands-on testing of GPS watches and wearables, and competing in triathlons at an international age-group level, tfk provides in-depth expert analysis of fitness technology for serious athletes and endurance sport competitors. See the gear tfk uses. ID
To me, comparing a MIP/Solar model (especially Garmin’s most efficient solar watch) with the Amazfit AMOLED/Solar doesn’t quite seem like a fair comparison; the watches are based on completely different concepts and feature sets. After all, Garmin draws on years of experience with MIP/Solar technology, whereas Amazfit is venturing into solar for the first time—and doing so as the first manufacturer to offer an AMOLED/Solar model. It’s a bold move. It remains to be seen whether this combination will catch on, but I hope other manufacturers feel inspired to follow Amazfit’s lead. That could really advance AMOLED/Solar technology.
it was hard to compare amazfit with anything using the same tech 😉 being the first of its kind
i chose the f9 because i suppose that would be the competing watch
i think the argument goes that solar on the front just cant provide enough juice to be meaningful when the is a juice hungry amoled display. that was definitely true. however going forward amoled displays get more efficient as do solar harvesting techniques.so yes i think you are right that this tech might pass to other brands. against that every coponent is getting so is solar needed? it’s pretty niche even today
i would assume that component suppliers do the r&d and production rather than amazfit.