ScottG wrote:
As others have said, it's going to be prewired (as are the 50/100A panels).
FWIW, I am running 10 awg Romex for 125' to my 30A outlet and then I use a 50' 10awg extension cord. I loose 2~3 volts at full power (leaving me 116VAC or more). So personally, I would just use the standard 10awg Romex unless your voltage at the panel is very low.
Standard Romex (as in NM-B wire) is not rated for direct burial use nor use in damp or wet locations. It should not be run outdoors, whether above or below ground, regardless of whether or not there is conduit being used, as those are at considered least damp and usually wet locations. I don't think it's generally rated for UV exposure, either.
There are cable types similar to NM-B that are rated for underground use (the most common being UF-B). "Romex" is not a class of wire cable, technically speaking, but a brand name, and there are various cable types sold under that brand. Informally, at least, it is very frequently used in a generic sense to mean NM-B wire, however.
