Anyone significant planning on new generation will also plan the interconnect at the same time, and that includes transmission capacity. There is no point in having your new generation completed if the interconnect isn't done. In fact the bank shouldn't (and probably is checking, though not always) let you get financing for the new generation if you have not verified that there is interconnect to use that generation. Thus plans for transmission is supposed to happen before you get to permits. Though depending on timelines you may start building on before the other.

You putting solar on your roof is not significant. Your whole neighborhood putting solar up should be significant, but odds are this is done by individuals who don't realize their collective action is significant.