I was thinking about creating a mod with a similar premise, but it would also affect offshore water pumps. I am not particularly interested in the solar panels, as I think that the offshore pump idea would be more interesting/balancing.

Are you interested in expanding your mod? Am I free to make my own version? I do not want to steal from your mod, and I am not greatly invested in my idea. Feel free to simply say "no".

What is your opinion?

You are free to use the code for free, I want more good interesting mods.

Ask me if you need help for this project.

Thank you. I will look in to it.

What is the purpose of the create_entity parameters fast_replace and spill? https://lua-api.factorio.com/0.12.35/LuaSurface.html does not list those parameters. Are there more parameters not listed? Also, why do the solar panels not go to 0?

I also fixed a bug. If a solar panel was damaged, and then the pollution levels changed, the health would be reset to max. Now it keeps the health.

I also would like to fix the noise and particle effects created when swapping panels. I plan to do this by making all solar panels not have those effects, but I will trigger them automatically when a player or robot places them. Is there some bug that gets in the way of doing this, or did you just not implement it?

Thank you again for letting me use your code.

I just checked, you are right, it does not support 0.

The first version was with 0 and was ok, but than the vanilla doesn't support the "0W" value anymore.

Please be sure that you use the latest version:
https://lua-api.factorio.com/latest/LuaSurface.html
https://lua-api.factorio.com/latest/LuaSurface.html#LuaSurface.create_entity

surface.create_entity{name=…, position=…, direction=…, force=…, target=…, source=…, fast_replace=…, player=…, spill=…, raise_built=…, create_build_effect_smoke=…, spawn_decorations=…} → LuaEntity

I've asked about the create_build_effect_smoke = false and it was added to the game.

Thank you!