PNNL

Electric utilities facing growing demand could meet reliability targets with less investment by accounting for a benefit that transmission planning often overlooks: the ability to share power within and across regions.

A Pacific Northwest National Laboratory (PNNL) report, Transmission Planning for Long-Term Reliability: Literature and Gaps Analysis, examines existing research and grid planning practices and identifies seven gaps in how planners account for transmission’s contribution to long-term reliability.

Traditionally, resource adequacy discussions focus on generation resources such as natural gas and hydropower plants. But studies show that connecting regions can improve their ability to meet electricity demand without the addition of generators.

Yet planners often only recognize that value after choosing a transmission project for other reasons—such as to alleviate overloads in the case of a contingency event—rather than deliberately seeking it when deciding what infrastructure to build.

That distinction matters as utilities prepare for increasing electricity demand, including from data centers, while managing weather and storm risks and the need to keep service affordable.

Why transmission planning matters for energy affordability

The principle is straightforward. Neighboring regions, and even areas within a single planning region, often reach peak electricity demand at different times. As a result, a region with surplus generation can help another meet its peak demand, provided the transmission system can deliver the power. The extent of the benefit depends on the resources, demand patterns, and connections of these regions.

Transmission can therefore enable planners to make better use of existing resources rather than requiring every region to build enough generation to meet its highest possible demand independently.

“You can keep the same generation mix in Region A and Region B and simply add a transmission line between them. In some cases, that transmission line alone can provide a capacity benefit without changing the generation mix or building new generation,” said Travis Douville, an advisor in Energy Systems Integration at PNNL. “Further, this effect may also be observed between sub-areas of a given planning region, so it is not limited to large-scale interregional transmission development.”

For households and businesses, the potential payoff is dependable electricity with less spending needed to provide it.

“You could achieve reliability targets with less investment,” Douville said. 

Centering reliability as part of transmission planning

To understand what prevents planners from capturing that value, researchers reviewed existing research, industry practices, and planning approaches used by major regional grid planning operators. Working with a group of industry experts, researchers identified seven key gaps that limit how transmission’s reliability benefits are considered in planning decisions. Those gaps arise in three areas: regional planning, interregional planning, and valuation.

Federal Energy Regulatory Commission Order 1920 requires transmission planners to evaluate and quantify seven specific transmission benefits, including resource adequacy, to help identify the projects that most cost-effectively deliver affordable, reliable, and resilient electric systems.

Grid planners can use the report to examine how their processes account for assistance from neighboring systems and identify questions to investigate when comparing transmission and generation investments. Regulators can use it to inform discussions about whether proposed investments fully reflect transmission’s reliability benefits.

That focus supports the Department of Energy Office of Electricity’s mission to deliver affordable, reliable, and secure energy. By clarifying what remains unknown, PNNL aims to help planners evaluate transmission’s role in meeting future demand while maintaining the reliability customers expect.