Size of wire for earth ground?

[Smeeg]

For earth grounding(ground rod pounded into earth) my small 400 watt 24v system at a cabin What gauge wire should I use for the 2000 watt inverter & 40amp charge controller? I’ve read one size smaller than my biggest wire so that would be 6awg. I emailed the inverter they said 12awg & emailed the charge controller they said 10awg?

 

[timselectric]

12 is fine. But 10 won't hurt anything.
If it's susceptible to physical damage. #6 minimum is usually required.