I have an outdoor solar equipment wall with 12 inverters feeding breakers of a combiner panel. A ground rod is to be installed for the equipment wall. My question is relating to the size of the EGC. 250.66(A) says if I use a ground rod my EGC only has to be #6 copper even though the ungrounded conductors feeding the panel are 600mcm AL which would indicate a 1/0 copper size for the EGC(Table 250.66). Any thoughts or ideas are more than welcome!
You are talking about the GEC, not the EGC.
The EGC is per 250.122.
The GEC is per 250.66 & 690.47.
In some cases, you can combine them and follow corresponding rules for both combined. But when the EGC has to be a lot larger than the GEC, IMO, you are asking for trouble to combine them. The EGC can simply be lug to lug, while the GEC has to be irreversibly connected (crimped, welded, etc).
It's not obvious, but 250.66 is an "OR rule", not an "AND rule". It provides the table, but allows you to ignore the table, provided you can meet any of options A through C.