Jeff Y wrote: Yes, I guess its possible a local county can make up their own rules, but I am not aware of any requirement in the NEC Jeff, this sounds like a job for Donuts! It sounds like their position is possibly based on a local requirement or perceived requirement, independent of the NEC. It is also possible that they have not adopted the 2008 NEC or become familiar with it yet. Either way, donuts sooth a savage beast... William Miller cited 2008 NEC 690.10 Stand-Alone Systems, which would be a good place to start. It specifically permits applications such as the one you described, as long as there is PV and the premises AC wiring is supplied via an inverter... (690 only applies to PV) There is an explanatory note in the NEC Handbook that helps drive the point home. I would backup (no pun intended) 690.10 with 2008 NEC 705 Interconnected Electric Power Production Sources. 705.2 Definitions describes your application as a Hybrid System. 2008 NEC 705.2 Definitions. Hybrid System. A system comprised of multiple power sources. These power sources could include photovoltaic, wind, micro-hydro generators, engine-driven generators, and others, but do not include electric power production and distribution network systems. Energy storage systems such as batteries, flywheels, or superconducting magnetic storage equipment do not constitute a power source for the purpose of this definition. I recommend studying up on 705 and making sure the proposed design complies before running down to the permit counter with donuts. In particular, a hybrid system does not include "Energy storage systems such as batteries", which basically means that as long as you are running the premises loads on AC, you should be fine. (The inverter output is the Energy Source for the loads). Best of luck to the homeowner! Matt Lafferty
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