Many people think their electricity begins and ends with the utility at the top of their monthly bill. However, when you flip a switch, your light is not powered by the nearest plant. It draws from a regional pool supplied by hundreds of generators spanning thousands of miles across the West. The western grid is a vast, interconnected web of transmission wires linking utilities, states, and the entire region into one shared system.

Exhibit 1: Regional transmission connects the western grid.

Western Interconnection balancing authorities and transmission lines.

RMI Graphic. Source: Western Electricity Coordinating Council, Department of Homeland Security.

Electrons take the path of least resistance, guided by the laws of physics — not state or utility boundaries. Utilities continuously adjust supply and demand, routing power to where it can serve customers most reliably and affordably. This constant, invisible balancing act is what makes the western grid so powerful: no state stands alone. In moments of crisis, states support each other to keep the lights on across the West. As our demand for electricity grows from increased manufacturing, new data centers, and more, we will need more generation — and more regional transmission.

A network of mutual support

Every western state shares power with its neighbors. As illustrated in Exhibit 2 below, most major utilities in each state acted as both electricity importers and exporters in 2024 (data for all 38 western balancing authorities). When one utility has more supply than it needs, that surplus automatically helps meet demand in neighboring areas. And, when a utility’s electricity demand spikes or generation dips, the grid taps into regional supply to avoid outages. In this shared system, everyone relies on and supports one another.

Power flows are dynamic

Power flows between states are dynamic, shifting with seasons, weather patterns, and market conditions. As an example, Exhibit 3 showcases the seasonal dance of electricity interchange between the largest utilities in Arizona and New Mexico. In the summer, Arizona’s electricity demand increases as residents combat the sweltering heat with air conditioning. Next door, New Mexico produces more electricity than it consumes, sending excess power to Arizona. As the temperatures cool in the winter, demand patterns shift, and flows reverse or become bi-directional, depending on where supply is cheapest and most available.

Transmission shines in crisis

The western grid works quietly in the background every day, but its true value becomes undeniable during grid emergencies. During severe weather, unexpected plant outages, or sudden demand surges, regional transmission can be the difference between the lights staying on and a widespread blackout. Exhibit 4 shows that in 2024’s most challenging peak hours, states relied on imports for up to 70 percent of their electricity needs.

Case Study: January 2024 Pacific Northwest Cold Snap

From January 11^th to 17^th, 2024, a multi-day cold snap pushed demand in the Pacific Northwest to peak levels. As the region declared a reliability emergency, neighboring states stepped in. The Northwest region imported about 4,700 MW on average during peak hours, primarily supplied by the Southwest and Rockies regions (see Exhibit 5). On January 13^th, when Seattle City Light reached its highest demand of the year, it maintained reliable service by importing 41 percent of its electricity from neighboring utilities (see Exhibit 4).

Case Study: July 2024 Montana Heat Wave and Generator Outage

Beyond the peak hour, extreme grid events can happen at any time of year. In July 2024, Montana was hit by a major heat wave and a fierce storm just as the state’s largest generator went offline. With local generation down and high cooling demand, NorthWestern Energy reached its 2024 peak import of 59 percent of its demand, until repairs and weather relief stabilized the system (see Exhibit 6).

Powering the West’s future

Stronger regional transmission is not just a win for just a few states — it’s the backbone of the western grid. Every state relies on and supports this shared system, ensuring reliable and affordable power for millions of homes and businesses across the West.

Looking ahead, the grid faces both challenges and opportunities. Rising demand from AI and manufacturing will require more generation — and more regional transmission. Fortunately, new projects such as Boardman to Hemingway, SunZia, Gateway, Greenlink, and SWIP North are coming online in the next few years. And, expanded regional market cooperation will strengthen utilities’ ability to share power more efficiently and cost-effectively.

To secure lasting economic growth, maintain energy affordability, and ensure long-term reliability, the West must continue investing in regional transmission planning and expansion. This is a win-win opportunity that benefits every Western state.