> There is also an argument to be made that the R&D isn't finished and it still makes sense to subsidize it to drive the cost down further.

Maybe there is an argument to be made, but it sounds like a very poor one if poor countries are now putting up solar panels because it's the cheapest form of energy production. Sounds like subsidizing the same panels going up on houses is a bit silly now that the costs have shifted so much.

The argument can probably be made for direct subsidies of R&D for bleeding edge solar tech, and perhaps even battery installations to get volume up. Or maybe even subsidizing local production vs. buying everything from China.

The arguments for wealthy countries to subsidize their wealthiest citizens to install solar for personal gain seems rather weak at this point in the game. It certainly made sense 20 years ago, but in most areas where it makes economic sense to begin with solar penetration has hit a tipping point.