Interesting, are you aware of anyone going off-grid for this reason? Where I live (Menlo), I don't think anyone would have a propane tank installed because of the size and unsightliness. The sound would also be annoying to them (and their neighbors, given how small the plots are). People generally build to the very edge of their property to maximize resale value, and this would take up a decent chunk of space. Maybe out in Woodside people would do this, since it's a bit more rural. Still, I've not heard of anyone saying the new income-based fees (which I disagree with, as noted above) are too high, and I'm going to install a propane tank and genearator. As you point out, this would go against the environmental rationale, which most folks with solar probably care a lot about. It's an interesting thought experiment though!