But decentralized green energy can be practical in certain situations. I put a large solar system onto my house and it'll take 14 or 15 years for it to pay for itself, assuming a 3% inflation rate on power rates. That's a low ROI compared to what I make in my real investments.
But it does help me reduce my monthly expenses as I shift towards retirement in a few years. Basically, in a year or two (a few years before I retire) I'll shift my investment portfolio from being 100% equities to being 70% equities / 30% bonds/treasuries/money markets. If it wasn't for the fact that some of my energy costs are "prepaid" by buying solar, I might have my portfolio lighter in equities: say 60%/40%.
Plus it helps me with my real purpose for going solar: avoid the uncertainty of energy inflation costs. That's my real reason for putting solar onto my house. Even if they raise my power rates sky high, because my solar produces about 2/3rds of the power I consume, I won't lose sleep over sky high rates. So my retirement budget can be a little smoother.
Only if you have goals like that is green energy worth it. And even then only if you're in an ideal environment (live in the south where we get lots of sun, use less heat in the winter because it's not hot here, metal roof so you don't have to replace it in 10 years, part of your roof facing south to catch more solar during the winter, etc.).