This report—Barriers and Opportunities To Realize the System Value of Interregional Transmission—examines the barriers and identifies potential opportunities within existing market and operating rules to achieve the benefits of coordinated transmission planning and operations for electric customers. This report is part of the U.S. Department of Energy’s (DOE’s) National Transmission Planning Study (NTP Study), conducted by the National Renewable Energy Laboratory and Pacific Northwest National Laboratory. The aim of the NTP Study is to identify transmission that will provide broadscale benefits to electric customers, inform regional and interregional transmission planning processes, and identify interregional and national strategies to accelerate decarbonization while maintaining system reliability.

The study describes the high benefit to cost ratio to adding interregional high voltage direct current transmission lines to the U.S. electric grid. Currently there are seven back-to-back high-voltage direct-current facilities enabling approximately 1 GW of electricity to flow between the Eastern and Western interconnections. This transfer capability between the interconnections is very small compared to the networks they connect—the larger Eastern interconnection is home to 700 GW of generating capacity, and the Western interconnect is home to roughly 250 GW of electricity.