Long-term load and DER forecasting is critical to achieve clean energy goals and ensure a reliable, resilient, and affordable energy system. This report, Long-Term Load and DER Forecasting, was produced by ESIG’s Long-Term Load and DER Forecasting Task Force and addresses key challenges in long-term load and distributed energy resource (DER) forecasting in today’s transforming grid.

Traditionally, long-term load and DER forecasts focused on total annual energy and peak demand. However, the evolving energy landscape—marked by variable renewable generation, unprecedented load growth from electrification (buildings, transportation, data centers, manufacturing), and rising customer-sited solar, battery storage, electric vehicles—necessitates a paradigm shift.

Traditional methods, which allocate load and DER growth based on proportional scaling of energy consumption, peak demand, or customer count, often fail to capture emerging geospatial adoption patterns. To accurately predict future energy demand requires explicit modeling of various demand-side modifiers to arrive at a net load forecast—including energy efficiency, solar, battery storage, economic growth, new customer business loads, electric vehicle charging, and building electrification.

The report outlines key elements of a more geospatially and temporally granular, scenario-based approach, including (1) high-resolution, time-based (hourly) forecasts to capture the correlated impacts of weather on demand, generation, and the nuances of DER behavior, and (2) methods that account for the underlying drivers of new sector demands and technology adoption, such as price signals and policy drivers.

Scenario-based forecasting approaches better equip planners across grid planning entities and within planning departments to assess a range of possible futures and provide opportunities for greater coordination across planning entities to improve system-wide preparedness.

While the challenges of long-term load and DER forecasting are complex and evolving, they present promising opportunities for innovation and improvement. As energy systems integrate new technologies, demand patterns, and policies, more advanced, geospatially and temporally granular forecasting methods are crucial for ensuring grid reliability and effective planning. By adopting a flexible, scenario-based approach and fostering better coordination across entities, energy planners can pave the way for a more resilient and efficient grid, prepared to meet the demands of tomorrow’s energy landscape.

Watch the Long-Term Load and DER Forecasting Webinar recording here.