[AnthonyMouse]

~25% was from the EIA as the US average for utility scale PV:

https://www.eia.gov/todayinenergy/detail.php?id=39832

Rooftop is presumably bringing down the US average, maybe there is more rooftop capacity in the north and utility-scale capacity in the southwest or utility-scale more often uses sun tracking. And as you point out solar output is quite dependent on latitude and clear skies.

> it's unrealistic to assume this number will ever meaningfully change for solar.

Well, sort of. Being dependent on all of those things means it would change depending on where the capacity is being installed and what kind. The world average is ~13% primarily because China + Europe represents around two thirds of current capacity and China has a shockingly poor capacity factor for its latitude whereas Europe has the expectedly poor capacity factor for its latitude -- how did China manage to get a lower capacity factor than Finland or Russia anyway?

But go install a lot more utility-scale capacity in the US Southwest, India, Australia, South America, etc. and the world average would move up by a non-trivial amount.