150 Amp Service Ground Wire Size. Maximum allowable ampacities for conductors in raceway, cable or earth (30°c) maximum allowable ampacities for conductors in free air (30°c) maximum. That would be called the neutral not ground.
For 150 amps in thwn wire size is 1/0, some municipalties allow you to go 1 size smaller, since it carries the unbalanced load, and that would. Grounding electrode conductor sizing (table 250.66); To make your a little easier for you, here are our top picks for these wire sizes: