It seems lack of transmission lines is holding back growth of the electrical grid in the US.  Adding new transmission lines is a very expensive prospect.  It looks like a good alternative would be to just replace the old, inefficient wires with newer technology.  This could quickly double the grid capacity at a relatively low cost.  It’s being called “reconductoring”.  From Oil Price:

Last year, a study from Lawrence Berkeley National Laboratory called “Queued Up” revealed that at the end of 2022, more than 10,000 power plant and energy storage projects (95% were zero-carbon resources) were waiting for permits to connect to the grid. That’s enough additional capacity to double the country’s electricity output, mostly from clean energy.

This Might Be The Fastest Way to Double U.S. Grid Capacity