[fghorow]

Your take is more sensible than the one I had. The community solar sells S units to somebody else, credits me with the monetary proceeds of the sale (and possibly a share of the associated Renewable Energy Credit proceeds), and charges me 90% of that "accounting fiction". They make money off the difference between the rates they invoice me for and the wholesale rates they actually sell the energy for (via a PPA or something).

I still argue that (N+S) units of energy are actually generated. The original generator of N units has no knowledge of the community solar arrangement, and is producing the N units of energy. Unless the community solar is lying about producing S units of energy -- remember, they are never disclosing S, only the associated monetary amount -- they too are selling S units to somebody else at a wholesale rate but getting their cash flow augmented by invoicing me. What a tangled web of cashflows!

I think that a PV array on the roof is preferable in situations where a purchaser is able to do that. Less financial engineering, and more physics! YMMV.