> The ROI of a large PV farm must be substantially better than a home scale install.

Actually, it's the other way around.

A rooftop solar doesn't require much: the land is already there (it's yours), there isn't any bullshit with permits, all you need is a ladder or a bucket truck, a few ultra cheap panels, an aluminum frame, an inverter and a few dozen feet worth of wiring.

A large scale solar farm however? The developer needs to find suitable land (challenging to do when competing against big ag), there's permit paperwork involved because solar farms ain't agriculture, they need to pay for a high voltage connection to the nearest substation, the huge ass panels need a really solid support construction that can withstand wind and weather and that needs a solid foundation as well, you need thousands of feet worth of wiring, complex and massive inverters, lightning arrestors, god knows what.

Oh and you get resilience against natural disasters for free on top of that. Some drunk driver plows into a power pole, some redneck shoots up some birds and kills the power line (yes, that happens so often that utilities release yearly reminders to please leave the birds alone), or a heavy storm / flood takes out entire substations for weeks, whatever - you throw the transfer switch, kill off all the non-essential consumers and can easily ride through a week worth of outage.