What an odd response! I never mentioned ICE so I suspect you're arguing against someone else.
The 40% "wasted sunlight" doesn't have a cost—sure, yes, kind of besides the point—but it also generates no electricity. That efficiency is further compounded by reductions in incidence by latitude, cloud cover, and time of day. The diminishment thus could be quite serious on any given panel or farm.
For combustion engines, a drop in efficiency increases your daily cost, and the carbon footprint.
For solar, it simply means a lower maximum energy storage per day, which implies a higher initial outlay. The "wasted" sunlight doesn't cost anything.