But the point is if "everyone" (or at least "many people") would run a solar farm - what would be the consequences? If solar mining costs decrease more, big solar (and other renewable energy) farms could emerge and would centralize the mining market again.
I'm not saying it's not a good concept, only would like to see more deep research on the topic.
I doubt bitcoin mining will be decentralised ever even if many people could arrange to obtain a free/low cost energy because simply the main problem after the cost of energy is the mining equipments
It is kinda similar to the video games, you need the latest graphic card to run the latest version of a game, but after few years...you have to buy a new graphic card again if you want to play the latest game
Well, having a renewable low cost energy is good and could reduce a little bit the decentralisation that's all