For solar power to make sense, there's one non-negotiable component...and yes, it's that bright, shiny thing in the sky - the sun. But just because your planet has a sun doesn't mean you should use solar power...
The best examples are places like Denver or SoCal, where the sun is out showing off most days of the year. Then you move on to places like New York, Toronto or Berlin - which have plenty of overcast days - and your case for using solar power goes out the window.
The point of all of this isn't to say that solar power can't be part of the energy solution, but there are still quite a few hoops we've got to jump through to get there.