Decarbonization policies, the accelerated integration of renewable energy resources, rising electrification demands, and the growing frequency and severity of extreme weather events, combined with unprecedented large-load interconnection requests and a heightened emphasis on system resilience, are fundamentally reshaping the electric grid. These dynamics create significant opportunities to transition toward a cleaner, more resilient system. However, they also introduce profound challenges for transmission planning, which must increasingly operate under higher levels of uncertainty, greater complexity, and evolving reliability requirements. In response to these transformative dynamics, transmission planning methodologies must adapt to account for a broader range of uncertainties while also balancing flexibility, cost-effectiveness, and system resilience. On behalf of the Midcontinent Independent System Operator (MISO), E3 recently released a whitepaper that outlines opportunities for the application of probabilistic planning methods that can support transmission planners in addressing the challenges of persistent uncertainty and accelerated change.
In our study, Probabilistic Planning Methods: A Review of Methods Available to Transmission Planners, E3 conducted a comprehensive review of methods for characterizing uncertainty, as well as their applications in power flow, production cost, and capacity expansion modeling. The review examined existing and emerging methods across ISO, RTO, and utility planning processes, as well as methods in use or under exploration in academia and industry. The overarching goal of the project was to outline actionable steps to enhance transmission planning processes, ensuring they remain robust and adaptable in the face of increasing uncertainty. The study provides insight into emerging methods that capture a wide range of uncertainty – driven by economic and policy changes as well as weather, climate change, correlated outage risks and system contingencies – while ensuring planners maintain a cost-effective and reliable electric system.
To inform the study, E3 conducted a series of interviews with experts and thought leaders across North America, which included ISO & RTO planning departments, academic researchers, and other industry practitioners, to discuss methods for addressing uncertainty. These discussions provided invaluable insight into addressing the uncertainty that transmission planners are facing, the methods that are being used and explored to overcome these issues, and potential barriers to stakeholder acceptance and implementation.
In partnership with MISO, E3 also co-hosted a symposium that brought together representatives from RTOs, utilities, and experts from national labs and academia to discuss new analytical techniques such as adoption of probabilistic methods that can address increasing complexity and help ensure a reliable, clean grid of the future.
Our study, released this week, summarizes key themes from the symposium as well as additional research on applications of probabilistic methods in transmission planning. We explore how transmission planning methodologies must adapt to account for a broader range of uncertainties in response to the transformative dynamics facing the electric power system. The study also considers that system planners need to ensure that decision-making for investments in transmission infrastructure, often characterized by long lead times, reflect a “least-regrets” approach, balancing flexibility, cost-effectiveness, and system resilience. This requires the adoption of methods that incorporate advanced scenario analysis, probabilistic modeling, and adaptive planning frameworks to guide infrastructure development under conditions of persistent uncertainty and accelerated change. Our study identifies opportunities for the application of planning methods that can support transmission planners in addressing these challenges.
Specifically, we offer four key recommendations for implementation of methods that layer probabilistic rigor into existing processes:
- Enhance the linkages between Power Flow and Production Cost Models
- Pre-process inputs using probabilistic methods to characterize uncertainty
- Adopt enhanced methods for assessing the economic cost of uncertainty
- Adopt stochastic scenario evaluation and risk assessment
We identify pathways to align planning practices with emerging grid needs, while enhancing transparency, comparability, and stakeholder confidence. We suggest this could take the form of a phased implementation of these recommendations through a hybrid approach that enhances, rather than replaces, existing planning frameworks. Additional details regarding these recommendations and other methods under exploration are provided in the Technical Report.
Download the report >
This report was prepared by Kevin Steinberger, Chris Herman, Lakshmi Alagappan, Edita Danielyan, and Will Beattie. For further information on E3’s work in transmission planning, please contact lakshmi@ethree.com.
