I remember reading somewhere on their website that the battery would last roughly a month if it was just in smartwatch mode, with 3 hours of direct sunlight solar charging per day. so yes, emergency “top up” charging basically. What this means for me in practice, is that I can use a watch face that utilizes a lot of battery power (comparatively), and with roughly an hour each day in direct sunlight during routine exercise I am able to go well over a week without even thinking about charging. What I end up usually doing, is taking it off my wrist after exercise to top up on the charger while I shower just because that is convenient. But I can and have gone well over a week both due to curiosity as well as travel. One less cord to worry about. That piece of mind is worth the extra $100 to me.