Three Grids, Seven Market Operators, and a West That Never Joined

The power grid course already walked through the machines: generation, step-up transformers, transmission, substations, distribution. It also covered the basic kinds of utilities and the seven big market operators in Who Runs the Grid. This course picks up where that one stopped. It is about the big lines being built across southern Idaho, who decides how power moves on them, and who pays for them. To follow any of that, you need a map in your head of how the West is organized, because it is organized very differently from the rest of the country.

Three grids that barely touch

The lower 48 states run on three separate synchronized grids, called interconnections. Inside each one, every large generator spins in step at 60 hertz. Between them, power moves only through a handful of limited ties. EIA describes them as operating "largely independently from each other."

Idaho sits entirely in the Western Interconnection. A kilowatt-hour generated at a dam on the Snake River is electrically in step with a gas plant in Arizona and a wind farm in Wyoming. It is not in step with anything in Kansas.

RTOs: a voluntary club the West mostly skipped

FERC's own history of market operators is short. In its open access orders of the 1990s it suggested independent system operators as one way for existing power pools to give everyone fair use of the wires. Then Order No. 2000 "encouraged the voluntary formation" of regional transmission organizations and listed twelve characteristics an RTO must have. The key word is voluntary. Utilities in the Midwest, Mid-Atlantic, New England, New York, Texas and California formed or joined RTOs and ISOs. FERC's list of them today has seven names: CAISO, ERCOT, SPP, MISO, PJM, NYISO and ISO-NE.

Most of the West outside California stayed out. Each large utility kept running its own balancing area, planning its own transmission and trading with neighbors through bilateral contracts. That is why the West has more balancing authorities than the much larger Eastern grid. And it is why the West's market changes, covered in lessons 2 and 3, come in pieces: a real-time market in 2014, a day-ahead market in 2026, a competing day-ahead market planned for 2027, and a new governing board seated in September 2026.

Who actually runs the grid in Idaho

Several organizations keep the lights on in different parts of the state. The ones that matter most for this course:

The market entry years come from the Western Energy Markets participant list. Co-ops and city utilities such as those that buy from BPA sit inside someone else's balancing area. Their power still moves on the same wires.

Hubs, paths and why two substations keep coming up

Transmission works as a network, but a few nodes carry far more weight than others. In southern Idaho, two of them come up in almost every big project.

• Midpoint substation, north of the Snake River in south central Idaho. Idaho Power describes it as near Jerome; the Idaho PUC's 2025 SWIP-N order says near Shoshone; press releases say near Twin Falls. Same place. SWIP-N ends here, and Gateway West segments run into it.
• Hemingway substation, in western Owyhee County. The BLM describes it as near Melba, about 20 miles southwest of Boise. Boardman to Hemingway ends here, and so do Gateway West segments from the east.

PacifiCorp's 2026 progress report to WECC lists an existing 500 kV Midpoint to Hemingway circuit, in service since July 2010, plus a planned second Midpoint to Hemingway circuit targeted for the fourth quarter of 2028. Put a new line into one of these hubs and you change what can flow across the whole southern Idaho corridor.

Checking the scale of a claim

Where does 13,000 MW come from? Brattle's market report for Great Basin says the Desert Southwest's winter peak runs about "13 GW lower than the summer peak." Lower demand isn't the same as surplus supply for sale, so ask Idaho Power how much of that it has contracted.