Garmin Instinct 3 Solar 45mm - 28 Days and 10 ATM

Garmin Instinct 3 Solar 45mm pairs a 45 mm case with up to 28 days of battery life in smartwatch mode and 10 ATM water resistance. Garmin says the solar models can run with unlimited battery life in smartwatch mode under bright outdoor conditions, and Best Buy lists the watch at $299.99 as of 09/09/2026.

Solar Watch, Two Sizes

The Instinct 3 Solar series arrived in 45 mm and 50 mm sizes, and Garmin introduced the lineup on January 6, 2025. The company also said the solar models start at $399.99 at launch, while the 45 mm model's battery life reaches up to 28 days in smartwatch mode and up to 40 hours in GPS-only mode.

Best Buy lists the 45 mm model with a 40 mm screen size, no touch screen, Android and Apple iOS compatibility, and 1 GB of built-in storage. The same listing shows a 45 mm fiber-reinforced polymer case, black band, and a 2025 model year.

Specs In Daily Use

Garmin's owner manual lists a rechargeable built-in lithium-ion battery, 10 ATM water rating, and an operating temperature range from -20 C to 60 C. The manual also says the 45 mm solar model can reach up to 130 hours in GPS-only mode with solar and up to 40 days in battery saver watch mode with solar.

The 45 mm watch sits below the 50 mm version in battery figures, which Garmin lists at up to 40 days in smartwatch mode and up to 60 hours in GPS-only mode. That makes the smaller model the lighter-duty choice inside the same line, while keeping the same solar charging approach and 10 ATM rating.

Where It Fits

Compared with the launch price of $399.99 for solar models, the $299.99 Best Buy price sits lower. For buyers who want the 45 mm size and Garmin's solar charging approach, the model keeps the core outdoor-watch package intact without moving into the larger 50 mm body.

Bottom Line For Buyers

Garmin Instinct 3 Solar 45mm is the more compact solar model in the 2025 Instinct 3 line, with a 45 mm case, 10 ATM water resistance, and up to 28 days of smartwatch battery life. It fits users who want a rugged GPS watch and can live with a monochrome, non-touch display.