A power line between two regions can be especially valuable when only one of them is short of supply. A Lawrence Berkeley National Laboratory study finds that staggered periods of high demand create that opportunity across parts of the United States, but power does not consistently travel toward the region under greater pressure.
Researchers compared net load and electricity transfers among 18 continental U.S. transmission planning regions from 2016 through 2024. They identified each region’s 100 highest net-load hours in a year, distinguishing hours when neighboring regions peaked together from those when only one did. In the latter case, the direction of the transfer provided an observable measure of support.
For roughly half of the connected regions studied, electricity traveled toward the high-need region only 50 to 60 percent of the relevant time, according to the lab. On some connections, the region facing a peak tended to reduce imports or increase exports even while its neighbor was outside its own peak. The benefit of a connection could also be much greater on one side than on the other.
What a transmission line can promise
A line’s rated capacity answers a physical question: how much power could cross? Crediting that entire amount in a reliability plan makes a further assumption about whether electricity will be available and sent in the needed direction at a particular hour. The researchers’ comparison puts those assumptions alongside an observable record.
Flow direction alone cannot diagnose an operator’s decision or establish that an outage was avoidable. What the historical comparison offers is a way to identify which connections deserve closer examination before planners count them as a substitute for local supply. A shared line need not carry equal insurance value for both of the regions paying for it.