So Garmin has added a solar coating to the glass face of the Fenix 7 which turns the sun’s rays into a boost to the battery, offering up to 5 days of GPS tracking and 5 weeks in smartwatch mode. That’s a lot of power hungry functions to keep running – a drain on your battery. That includes not just GPS tracking, but Bluetooth, ANT+ and WiFi connectivity, optical heart rate measurement and pulse oximetry (measuring the oxygen level in your blood). The Garmin Fenix 7 Sapphire Solar packs a lot of functionality into a watch-sized package.

Read more: Garmin Forerunner 255 smartwatch full review So if you want mapping and a brighter, crisper, prettier display it might be worth spending a bit more. Since it's a mid-range GPS watch, the other thing the 255 lacks is an AMOLED touchscreen - it has a transflective memory-in-pixel LCD type.

There's no danger of the Forerunner 255 replacing your cycling head unit since it doesn't have mapping, but if you're already in the Garmin ecosystem with your bike computer and just want to add health monitoring without spending a fortune, the Forerunner 255 has the majority of it covered. Most obviously it lacks mapping, but it does use the same multi-band GPS for activity tracking as the more expensive Garmin watches and it has the same wrist-based heart-rate monitor, enabling the same health monitoring that includes sleep monitoring, heart rate variability, training stress and VO2max estimates. The updates the Forerunner 255 received were huge when it launched in 2022, putting it up there in functionality terms virtually on a level with its big brother the Garmin Forerunner 955 as well as the Garmin Fenix 7 and Garmin Epix 2.

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