The National Renewable Energy Laboratory (NREL) has published a guide to understanding the integrated resource plans (IRPs) that utilities prepare to project the generating capacity they will need in the future. Most states require utilities to develop IRPs, as shown in the map below reflecting requirements as of March 2022.

NREL’s guide was requested by the National Association of State Energy Officials (NASEO), the National Association of Regulated Utility Commissioners (NARUC) and the U.S. Department of Energy.

To develop an IRP, a utility uses a power system model together with data inputs and assumptions. A utility’s data, assumptions and modeling approach are often challenged by state regulators, solar trade groups, and nonprofit groups that make a case for including more solar and storage in the plan to achieve a least-cost, reliable system.

NREL says the guide “can help planners and stakeholders understand power system model results and ask the right questions of utilities” when reviewing utility resource plans. The guide is divided into beginner and advanced levels.

NASEO requested the guide to support state and territory energy offices in their work with the private sector “to accelerate energy-related economic development and support meeting state energy goals,” said Kirsten Verclas, NASEO senior managing director for electricity and energy security. To conduct that work, staff “need to have a profound understanding of energy modeling” and how utilities use models to plan for the “grid of the future,” she said.

Verclas said NASEO hopes the guide will enable energy offices “to ensure that utilities’ modeling approaches include state energy goals.”

Maggie Shober, research director for the Southern Alliance for Clean Energy, said that integrated resource plans “are notoriously difficult to understand, let alone engage in.” The NREL guides will help SACE make resource planning “more accessible to everyone,” she said. That could help regulators be more responsive to what members of the public are interested in, she said, such as deployment of solar and storage resources “at an accelerated pace and in an equitable manner.”

Wesley Cole, an energy analyst with NREL and point person for the guidebook project, said “more people are engaging in the utility planning process than ever before, and many are new to planning the grid with resources such as wind and solar.” He said the guide, beyond helping people “get up to speed,” can also “help everybody because it should lead to better decisions in the end.”

Three states have taken a step further on resource planning, as Arizona, New Mexico and Michigan now require utilities to make their resource modeling transparent. Those policies follow a proposal put forth by Anna Sommer, a principal of the consulting firm Energy Futures Group, for states to require transparent modeling to save consumers money. Under her proposal, each utility preparing a resource plan would provide to the state and selected intervening parties the data sets it used, a license to use the same model that it used, and a manual for that model.

The two-part NREL guide to resource plans is titled “Understanding Power System Model Results for Long-Term Resource Plans.”

The nonprofit Regulatory Assistance Project previously published a guide to integrated resource plans.