Policy-driven transmission expansion enhances US decarbonisation but requires careful planning

Policy choices to accelerate interregional transmission in the United States will shift the geography, cost and emissions outcomes of decarbonisation, but they do not remove trade-offs between least‑cost planning and resilience to extremes, according to a body of recent studies and sector reviews.

According to the original report in Nature Energy, congressional proposals that actively drive interregional transmission buildout increase transfers across regions by about 68% compared with baseline planning. The policy‑driven expansion improves the system’s ability to share surplus low‑cost renewable energy during periods of tight supply, materially strengthening reliability during extreme events. The Nature Energy analysis therefore frames transmission policy as an instrument for both decarbonisation and risk management, rather than purely a cost‑minimisation lever.

Industry and modelling evidence shows why those trade‑offs arise. NREL scenario work and supply‑side studies show that the cheapest pathways to very high shares of renewables tend to concentrate builds in the best resource regions and pair those with targeted transmission reinforcements. The Nature Energy authors note that a least‑cost approach focused on central US builds, or optimised siting of wind and solar together with selective line reinforcements, can deliver greater system‑wide savings and lower CO₂ emissions than broadly prescriptive, policy‑driven siting everywhere at once. NREL’s Standard Scenarios and 100%‑clean analysis provide similar conclusions: transmission clearly lowers system costs and enables more renewable deployment, but routing and siting decisions materially influence the magnitude of those savings.

At the same time, aggregated reviews of technology and cost trends underpin the case for expanded transfer capability. IRENA’s 2022 assessment of renewable generation costs shows continued declines in levelised costs for utility‑scale solar PV and onshore wind, reinforcing the economic rationale for transmitting power from high‑quality resource regions to load centres. U.S. data on construction costs reported by the EIA also indicate falling build costs for wind and solar in recent years, which increases the value of access to remote, high‑capacity‑factor sites. The implication for industrial decarbonisation is straightforward: cheaper renewable energy plus more transmission expands low‑cost clean power available to large industrial loads, but the magnitude depends on how and where lines and generation are built.

Policy design therefore matters. The Nature Energy study stresses that congressional directives that accelerate interregional lines without incorporating least‑cost siting or regional optimisation can raise overall system costs and, in some scenarios, produce higher emissions than more targeted expansion plans. At the same time, federal direction can shorten permitting timelines and reduce coordination failures that historically delay long‑distance projects, factors that the Department of Energy’s recent national transmission assessments identify as critical bottlenecks. According to the original report, the principal trade‑off is between centrally mandated, rapid network scaling that prioritises resilience and equity objectives, and planner‑led, cost‑optimised expansion that squeezes total system cost and emissions.

Reliability and extreme‑event resilience are central to the argument for broader, policy‑led transmission. The Nature Energy authors find that during extreme weather and other system shocks, larger interregional capacity allows imports to substitute for locally constrained supply, reducing unserved energy and emergency actions. This complements economic studies showing the value of interconnection in smoothing variability across large geographic areas, and modelling that highlights transmission’s role in reducing the need for costly local firming resources. For industrial consumers, lower risk of outages and more predictable access to low‑carbon supply can be as important as levelised cost reductions.

Yet implementation challenges remain. Academic and policy analyses emphasise the importance of coordinated regional planning, cost allocation mechanisms, and streamlining of permitting. Historical case studies and recent policy reviews show that the benefits of long‑distance HVDC and AC corridors materialise only when routing, financing and regulatory incentives are aligned across states and regions. Economic research also underscores that corporate profits and market dynamics can shift with new transmission, creating distributional tensions between incumbent generators, new entrants and load centres that lawmakers must address.

For industrial decarbonisation practitioners, the synthesis of recent literature suggests three practical takeaways. First, transmission expansion is necessary to realise deep decarbonisation at least cost and to deliver large volumes of low‑cost renewable energy to energy‑intensive industry. Second, how expansion is pursued, centrally mandated corridors versus optimised siting, will determine net system costs, emissions outcomes and the degree of resilience achieved. Third, policy packages that combine accelerated permitting, robust cost‑allocation rules and targeted siting incentives are more likely to capture the upside of increased interregional transfer capacity while limiting adverse cost and distributional outcomes.

In sum, the evidence indicates that policy‑driven transmission expansion can materially improve resilience and enable greater renewable sharing, but it is not a substitute for careful, least‑cost planning and regional cooperation. Industry data and modelling show that achieving both low cost and high reliability will require coordinated design choices on siting, financing and regulation so that expanded interregional capacity delivers predictable, affordable and low‑carbon power to the factories and facilities central to the United States’ industrial decarbonisation agenda.