I have also gone down the solar rabbit hole! from 830 to 1040 solar...my main reason was to get a bigger display🥸, and the solar was the only one locally available.
So now after 3 weeks, in the Middle East nogal, I can tell you that if you are a local weekend warrior and maybe have a few more rides during the holidays, then solar is a waste. I commute every day and do longer rides on the weekends and I do see some benefit...very small. But now its coming winter, in and out from work, I get no solar at all...of course.
Also during normal daytime rides, the unit is in your shadow a lot of the time and you can see from the widget how the charge fluctuates as it goes in and out of shadows.
One last very frustrating issue: when you switch off the unit, it says place it in direct sun to get a solar charge! Nope, big nope...it is so sensitive to temperature that it will inevitable overheat and stop any solar charging. Also, no Garmin person will actually admit that solar charging does not work while it is off, despite the marketing or manuals.
However, if you do long rides like bike packing then there for sure will be some gain...from what I understand the solar actually runs the device and any excess charge goes to charging the battery. But it will mean long hours in the saddle! In the blazing sun, at midday, mostly...so yeah...
I'm happy I got mine but only for the bigger display.
