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Lesson 2 of 8 · about 16 minutes

SWIP-N on the Ground

You'll be able to

  • State SWIP-N's length, voltage, endpoints, capacity split and schedule as of October 2026
  • Explain what PUC Order No. 36874 decided and what it deferred to a later cost case
  • Identify the local land-use and tax questions a transmission line raises
  • Estimate Idaho Power's share of the line from the ownership and capacity figures
  • Explain why CAISO, California's grid operator, is SWIP-N's main customer and what that means for who pays and who decides

SWIP-N is a grid project with a regional purpose, and the western grid course covers that side in depth. This lesson stays local: what a 500 kV line means for the ground it crosses in southern Idaho, what state regulators decided, and what they left for later.

The facts, as of October 2026

ItemFigureSource
RouteMidpoint Substation (the PUC and the 1994 BLM decision place it near Shoshone; Idaho Power says near Jerome; CAISO says near Twin Falls) to Robinson Summit Substation near Ely, NevadaT&D World, Sept. 2026
Length and voltage285 miles, 500 kV; the full Southwest Intertie corridor runs 576 milesT&D World
CostMore than $1 billionT&D World
CapacityOver 2,000 MW both directions; 500 MW northbound for Idaho PowerT&D World; Order 36874
Developer and operatorGreat Basin Transmission, an LS Power affiliate; capacity rights shared by the California ISO, NV Energy and Idaho PowerT&D World
Idaho Power's stakeAbout 11.4 percent ownership (250 MW) plus 250 MW more of capacity rightsOrder 36874
State approvalCertificate of public convenience and necessity, Order No. 36874, Dec. 12, 2025Idaho PUC
ConstructionBegan summer 2026; groundbreaking Sept. 3, 2026 in Ely; about 300 construction jobs; completion expected 2028T&D World

Most of the line is in Nevada. T&D World reported more than 70 percent of it there, which leaves less than 30 percent for Idaho: 285 x 0.30 = 85.5, so fewer than about 86 miles. Jeff Pierson's Feeding the Beast reporting puts the Idaho portion at 76 miles, which fits inside that limit.

What the PUC decided, and what it did not

The certificate answered one question: is Idaho Power's participation in the public interest? The commission said yes, for the 500 MW of northbound capacity. It did not decide what customers will pay.

Order 36874 says plainly that the commission made no finding on the prudence of any cost, and that Idaho Power did not ask for binding ratemaking treatment. Recovery waits for a future filing. The commission said it expects a full accounting there: final installed costs, every cost item, and documentation for any overrun or change from the plan. Staff described protections written into the agreements, including lower build-transfer fees if costs run over or the line is late, and, if the California ISO drops out, six months for Great Basin to present a plan to finish construction by October 1, 2029.

For residents, that means the money fight hasn't happened yet. The cost case is where ratepayers, irrigators and anyone else can test what Idaho Power spent.

Example: what is Idaho Power's share worth?

The order does not state a dollar figure, so treat this as a rough bracket, not a cost.

  • Ownership share: 11.4 percent of a project reported at "more than $1 billion." At exactly $1 billion: $1,000,000,000 x 0.114 = $114 million.
  • Jeff Pierson's reporting uses $1.09 billion. At that figure: $1,090,000,000 x 0.114 = about $124 million.
  • The second 250 MW is a capacity right, paid for under the agreements over time, not owned. Its cost shows up as payments, not as plant on the books.

So Idaho Power's owned piece likely lands somewhere above $114 million, before overruns. The real number will be in the recovery filing. Write down the bracket now and compare it when the filing arrives.

The local land-use questions

A 500 kV line is large: tall lattice or tubular towers, wide cleared corridors, access roads and staging yards. Where the route crosses BLM land, the BLM grants the right-of-way under 43 U.S.C. 1761, which covers "systems for generation, transmission, and distribution of electric energy." Where it crosses private or state land, the developer needs easements from owners and whatever local permits the county requires.

The local questions worth asking are concrete:

  • Towers and easements. Where exactly do towers sit on private ground, and what does the easement allow: future lines, herbicide use, access at any hour?
  • Roads and traffic. Which county roads carry heavy equipment during construction, and who repairs them? A road-use agreement should say.
  • Fire. Construction and maintenance in cheatgrass country carry fire risk. Ask for the fire plan and who pays if a fire starts on the right-of-way.
  • Weeds and reclamation. Disturbed ground grows cheatgrass fast. Ask what reseeding is required and for how long it is monitored.
  • Taxes. Idaho Code 63-405 has the State Tax Commission, not the county assessor, assess utility operating property and apportion it among counties. The statute now also apportions a kilowatt-hour tax on rate-regulated electric utilities by each county's share of 2025 property taxes on those companies, so a county should not assume new utility-owned line adds to its share the way new private property would. How SWIP-N's owners are classified decides how much reaches each county. Ask the assessor and the commission before anyone promises a tax windfall.

Idaho Power's outreach promises that the line "will generate new property tax revenue for counties and schools." Pierson's Point by Point Rebuttal Part 2 makes the counter-case: no one has set that tax revenue against the decades of rate-base recovery customers will pay on the same assets. Ask Idaho Power for both figures for your county, side by side. If it can't give them, say so.

Why the line keeps coming up

SWIP-N connects to the Midpoint Substation, one of the main hubs on Idaho Power's system, and adds a path south. Big generation projects in the Magic Valley were planned with it in mind. Jeff Pierson's Feeding the Beast No. 1 quotes a December 2023 California ISO planning document calling SWIP-North the only active proposal giving direct access to Idaho wind. That's why opponents of large wind and solar projects watch the line: it changes where developers can sell power.

The other side has a real argument too. The PUC accepted that 500 MW of winter import capacity helps Idaho customers during the season when solar is weakest, and Feeding the Beast No. 1 reports that commission staff called it a "least-cost, least-risk option" for identified capacity needs. Both things can be true: the line helps Idaho Power at winter peaks, and it makes the Magic Valley more attractive to developers selling power south.

Idaho Power's own plans moved on this line. Its 2023 resource plan left SWIP-N out of the preferred portfolio because its "potential involvement in the project remains uncertain." Its 2025 plan, acknowledged by the PUC in Order No. 36937 on February 17, 2026, includes it, online November 2028. The same utility also won a certificate in Order No. 36958 (March 10, 2026) for the Bennett gas expansion near Mountain Home: up to 167 MW from nine reciprocating engines, due June 2028. Imports and local gas are both in the plan.

Why CAISO matters on the ground here

The biggest buyer on SWIP-N is California's grid operator. The California Independent System Operator, or CAISO, funds 77.169 percent of the line and takes operational control of that share of its capacity, according to CAISO's 2024 board memo. Idaho Power's piece is the 500 MW northbound block described above. The western grid course covers what CAISO is and how it pays for lines and the full SWIP-N deal.

Who pays follows the same split. CAISO's share goes into its Transmission Access Charge, a FERC-approved rate billed to the utilities serving customers in CAISO's area, which covers about 80 percent of California and a small part of Nevada. Idaho customers pay only for Idaho Power's share, and only what the Idaho PUC allows in the future cost case. So most of the towers going up in southern Idaho will be paid for by people who will never see them.

The decisions that matter most for the CAISO block are made far from here. What flows south depends on CAISO's markets and on the resource portfolios California's utility commission feeds into CAISO's planning. CAISO's board is appointed by California's governor. Residents here have no vote on it. The places where local people do have a say are the county permit conditions on construction, the Idaho PUC case on Idaho Power's costs, and public comment in CAISO's planning process, which is open to anyone.

The dockets to watch are concrete. At the Idaho PUC, case IPC-E-25-08 and Idaho Power's coming cost-recovery filing. At CAISO, the annual transmission plan, with a draft each spring and a board vote in May, and whether Idaho wind stays in the portfolios it studies. At FERC, docket ER25-2025, where Great Basin's transmission rates for the CAISO share are set. And keep October 1, 2029 in mind: PUC staff said that if CAISO drops out, Great Basin has six months to present a plan to finish construction by that date, or the participation agreement may be terminated.

Common mix-ups

  • Claim: The PUC approved charging customers for SWIP-N. What the evidence shows: It approved Idaho Power's participation. Cost recovery and prudence wait for a future case.
  • Claim: SWIP-N was cancelled with Lava Ridge. What the evidence shows: Construction began in summer 2026, with a September 3 groundbreaking.
  • Claim: Idaho Power owns half the line. What the evidence shows: It owns about 11.4 percent, worth 250 MW, and holds rights to another 250 MW.

Reporting angle

  • Watch the Idaho PUC for Idaho Power's SWIP-N cost recovery filing. Compare its numbers with the commission's list of expected documentation in Order 36874.
  • Ask the county road department for any road-use or haul-route agreement with Great Basin Transmission or its contractors. Request it under Idaho Code 74-102.
  • Ask the county assessor and the Idaho State Tax Commission how SWIP-N will be assessed under Idaho Code 63-405, and what share the county expects.
  • File a FOIA request (5 U.S.C. 552) with the BLM for the right-of-way grant's stipulations on fire, weeds and reclamation for the Idaho segment.
  • Ask Idaho Power what happens to the 2029 and 2030 capacity math in IPC-E-26-04 if SWIP-N slips past 2028.
  • Track CAISO's annual transmission plan and FERC docket ER25-2025 for the CAISO share of SWIP-N: the revenue requirement, the in-service date and any sign CAISO might drop out, which would start a six-month clock for a plan to finish construction by October 1, 2029.

Research angle

Check yourself

1. What did Idaho PUC Order No. 36874 (December 12, 2025) decide about the cost of Idaho Power's share of SWIP-N?

2. How much northbound capacity does Idaho Power get from SWIP-N under the approved arrangement?

3. T&D World reported that more than 70 percent of SWIP-N's 285 miles are in Nevada. What is the most that could be in Idaho?

4. Who assesses the taxable value of utility operating property such as a transmission line in Idaho?

5. When did construction of SWIP-N formally begin, and when is it expected in service?

Terms in this lesson

SWIP-North
The northern segment of the Southwest Intertie Project, a 285-mile, 500 kV line from the Midpoint Substation near Twin Falls to Robinson Summit near Ely, Nevada.
Prudence review
A utility commission's later check on whether costs were reasonably incurred, which decides whether customers pay them.
Bidirectional capacity
A line's ability to move power in both directions, rated separately for each direction.
Operating property
Property a utility uses to deliver service, assessed for tax by the State Tax Commission instead of the county assessor.
Transmission Access Charge
CAISO's per-megawatt-hour charge, paid on load in its area, that recovers the FERC-approved costs of lines under its control, including CAISO's share of SWIP-N once in service.

Full glossary

Sources