There is no accurate estimate that I have seen, but there are processes, and I can provide links to some my earlier papers and point you to some future papers that I will post in the next few weeks that might help you understand these. Note that I tend to focus on my home state (California) with these, but the processes should be similar elsewhere in the U.S.
Let's start with the transmission network. About a year and a half ago, I posted a six part series on the California Independent System Operator (CAISO). Part 2 of this, section 3.1 described the CAISO Planning Process. There is a link below to this part.
However, California coordinates with the Western Electricity Coordinating Council (WECC) and the other states therein in their planning process. Furthermore there is a related process called Reliability Coordination, and the entity responsible for this is the Reliability Coordinator. CAISO recently took over this responsibility for most of WECC. I will need to send you through two links for this. The first is part 6 of the CAISO series, section 4. The transition to CAISO as the Security Coordinator was in process when I wrote this series, so I wrote a later update, which is the second link below (read it after the section 4).
Now distribution: There is also a process that relates to the distribution system, called resource adequacy. There is a link below to a paper on this and other related subjects.
Although the above processes are specific to California, I expect they will be in the future for much of the U.S.
Also there that many choices and many constraints when upgrading distribution systems. PG&E is currently restructuring, and one of the steps they are taking to mitigate the impacts of Public Safety Power Shutoffs is to implement a large number of microgrids in their service area. I'm starting a two-part post next week on their reorganization, and part 1 (to be psted next Tuesday) will cover these microgrids (among other subjects).