Honestly I never got the "solar power" concept as it applies to calipers and the like. I don't know about you but my shop has a roof, and lighting is so so inside.
I have three pairs of regular Mits and the batteries (LR77) last at minimum 1.5 to 2 years, with daily usage. I don't know the price difference battery versus solar, but I would to venture to guess the solar cost a tad bit more.
Another little factoid; when you turn the caliper off, the only thing that is switched off is the display the screen. If for example when the instrument is switched off say at 0.0. Move it an inch out 1" and turn it on the display when turned back on will read 1".
I saw video where the draw on the battery was measured. The current draw for all intensive purposes was the same on or off (within a milliamp or 2).
I know you are thinking "Oh you saw it on you tube so it must be true.". Having a fair amount of EE training I can tell you the guy's set up to do the measurements was sound. Personally I wouldn't want "Solar" powered metrology anything for the following reasons:
Just another thing to flake out.
Probably cost a bit more.
When I go to do a measurement I just want pick up my calipers and measure, not screw around trying to find adequate light, then wondering is it powered enough to give me an accurate reading.
So unless you drive a powder blue Prius, re-cycle your toilet paper, and live in a house made of recycled tires. Just buy a good pair of Mits, and ignore the marketing wenk.