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Courses › Western Grid Projects: CAISO, Markets, SWIP-N and Hemingway

Lesson 5 of 9 · about 19 minutes

SWIP-N: Who Owns It, Who Runs It, Who Pays

You'll be able to

  • State SWIP-N's endpoints, length, voltage, cost estimate and schedule as of October 2026
  • Explain the 77.169 and 22.831 percent split and what each party gets
  • Summarize the Idaho PUC certificate case: who took part, what they argued and what was decided
  • Weigh the evidence on whether SWIP-N is tied to Idaho wind for California

SWIP-N is a 285-mile, 500 kV line from Idaho Power's Midpoint substation in south central Idaho to the Robinson Summit substation near Ely, Nevada. At Robinson Summit it connects to lines already built: the One Nevada line south to the Harry Allen substation near Las Vegas, and DesertLink on to the Eldorado Valley. The developer, Great Basin Transmission, an LS Power affiliate, says the full corridor will run 576 miles and carry more than 2,000 MW in both directions. Construction began in summer 2026, with a groundbreaking in Ely on September 3. Completion is expected in 2028.

That paragraph is where the agreement ends. Everything else about SWIP-N is argued: who it is for, who carries the risk, and what it will lead to. The local permitting fight, including Jerome County's, is in lesson 6. The other course on this site, SWIP-N on the Ground, covers taxes, roads and weeds. This lesson is the regional deal.

The facts, as of October 2026

ItemFigureSource
EndpointsMidpoint (Idaho) to Robinson Summit (Nevada)PUC Order 36874; T&D World
Length, voltageAbout 285 miles, 500 kV; more than 70 percent in Nevada; 76 miles in IdahoT&D World; Idaho Power
Cost estimate$1,230 million nominal, excluding financing (CAISO, 2024); "more than $1 billion" (developer, 2026)CAISO memo; T&D World
Total capacity2,190 MW total SWIP, per Idaho Power's filing; developer says more than 2,000 MWOrder 36874; T&D World
CAISO share77.169 percent of funding, for southbound and certain northbound entitlementsCAISO memo
Idaho Power share500 MW northbound: 250 MW owned (about 11.4 percent ownership) plus 250 MW of rights from GBT NorthboundOrder 36874
Idaho approvalCertificate granted December 12, 2025Order 36874
FederalDOE selected the project for Transmission Facilitation Program capacity contract negotiations, April 25, 2024; BLM approved the Robinson Summit substation expansion November 20, 2025LS Power; BLM
Path rating2,070 MW north to south; 1,920 MW south to north (WECC rating cited by CAISO)CAISO transmittal letter, Nov. 22, 2024
Idaho Power ownership11.415 percent (250 MW northbound), plus a 40-year capacity entitlement for 250 MW more, with an option to buy it at the end of the termFERC, 193 FERC ¶ 61,094
Idaho Power planNot in the 2023 IRP preferred portfolio; in the 2025 IRP preferred portfolio, online November 2028PUC Orders 36233 and 36937
In serviceDeveloper: 2028. Idaho Power's page: 2029T&D World; Idaho Power

Note the last row. The developer says completion in 2028; Idaho Power's own page shows a 2026 to 2029 construction period and a 2029 in-service date. Ask both which date the power supply plan relies on.

A long history in two acts

SWIP started with Idaho Power in the late 1980s. Public scoping for the environmental review began in March 1989, the final EIS came out in July 1993, and the BLM's Record of Decision in November 1994 granted Idaho Power a right-of-way of roughly 540 miles. Idaho's land-use plans needed no amendment; Nevada's and Utah's did. That 1994 grant is why residents call these 30-year-old permits. In 2005 Great Basin Transmission acquired exclusive rights to the grant, according to LS Power's 2010 presentation to the Nevada Legislature, and in 2008 it ran an open season offering up to 1,850 MW in each direction. In the 2016-2017 and 2018-2019 planning cycles, SWIP-N was submitted as an Interregional Transmission Project to CAISO, NorthernGrid's predecessor NTTG and WestConnect. None of them selected it through that route.

The southern half got built first. One Nevada went into service in 2014 and DesertLink in 2020, according to the developer. The northern half, into Idaho, sat for years without a buyer.

The buyer turned out to be California. CAISO's board approved SWIP-N on December 14, 2023, in Addendum 1 to its 2022-2023 transmission plan, calling it "a joint regional policy-driven project with Idaho Power." The cost estimate then was $1,090 million. Its September 2024 memo explains why: California Public Utilities Commission resource portfolios identified 1,000 MW of Idaho wind for import into the ISO, and SWIP-N was "the sole known transmission project" that would give California buyers access to it by 2027. FERC accepted the development agreement between Great Basin and CAISO on January 21, 2025.

The split

The deal divides one physical line into two blocks run under two sets of rules.

  • CAISO block: CAISO funds 77.169 percent of the project, and Great Basin places those entitlements under CAISO's operational control as a participating transmission owner. Great Basin's application covered 1,117.5 MW southbound on SWIP-N and the One Nevada line, and 572.5 MW northbound. Cost recovery runs through CAISO's FERC transmission rates.
  • Idaho Power block: 22.831 percent, 500 MW northbound, held through GBT Northbound, an LS Power affiliate. Idaho Power owns 250 MW of it outright and has rights to use the other 250 MW. Its costs go to Idaho customers only through a future Idaho PUC case.

Example: checking the split

  • Idaho Power's filing: 500 MW is 22.83 percent of total SWIP capacity of 2,190 MW. Check: 2,190 x 0.2283 = 499.98 MW. It holds.
  • Ownership: Idaho Power's 250 MW is described as about 11.4 percent. Check: 250 / 2,190 = 0.114. It holds.
  • CAISO's dollar share of the $1,230 million estimate: 1,230 x 0.77169 = about $949 million.
  • The 22.831 percent block: 1,230 x 0.22831 = about $281 million. Idaho Power owns about half of that block's capacity (250 of 500 MW), and pays fees for the rest, so its owned share is roughly $140 million before overruns and financing.

These are proportional estimates. Real costs come in the recovery case. Write the bracket down now so you can compare it then.

The Idaho PUC case

Idaho Power filed case IPC-E-25-08 on March 7, 2025. Order No. 36874 lays out who said what.

PartyRolePosition
Commission staffPartyApprove. Without SWIP-N, capacity deficits of 123 MW in 2027, 154 MW in 2028, 384 MW in 2029. Called it a least-cost, least-risk option compared with an alternative 200 MW gas plant. Flagged risks: winter availability of Southwest power, permitting delays, CAISO termination, federal tax law changes.
Idaho Irrigation Pumpers AssociationIntervenorDeny, or limit recovery to completed projects and modeled costs. Raised overruns, stranded capacity, missing decommissioning and tax costs, and reliance on CAISO as anchor tenant. Said modeled need was 48 MW in 2028 and 86 MW in 2029, and less than 20 percent of the capacity would meet peak demand.
Micron TechnologyIntervenorThe order does not describe its position.
Stop Lava Ridge, Inc.CommenterFails the necessity test, not in Idaho's interest, would raise rates, unacceptable abandonment risk.
Rep. David J. LeavittCommenterDeny, or hold the case until the Legislature acts.
PublicComments28 timely: 11 support, 17 opposed; 7 late. Opposition cited rates, power going to California, renewable development, and views from the Minidoka National Historic Site. St. Luke's Health System supported.

The paperwork trail runs like this. The PUC gave notice of the application in Order No. 36541 on April 15, 2025. Order No. 36800, served October 9, 2025, scheduled a virtual workshop on October 21 and an in-person customer hearing on October 23 at the American Legion hall in Twin Falls; it did not start the case. Staff's support rested on Idaho Power's own AURORA modeling, which compared portfolios with and without SWIP-N; staff wrote that it "shows a substantial NPV savings for a resource portfolio with SWIP-North." The order never mentions Brattle. In January 2026, Order No. 36903 awarded the irrigators $14,525.70 in intervenor funding, to be recovered from Idaho Power's irrigation customers.

Idaho Power replied that it had most permits, that capacity transfers only at commercial operation, and that SWIP-N is a transmission-only project "entirely independent of" the Lava Ridge and Salmon Falls wind projects. The commission granted the certificate on December 12, 2025, and said it lacked authority over the broader policy and legal matters commenters raised.

Is it a wind export line?

This is the central dispute, and both sides have documents.

The case that SWIP-N is tied to Idaho wind for California rests on CAISO's own words. Its 2024 memo grounds the approval in 1,000 MW of Idaho wind in California's portfolios. The developer of Lava Ridge, Magic Valley Energy, is also an LS Power company. Opponents read that as one company building both the generation and the road out.

The case against rests on what changed and what Idaho Power holds. Interior moved on August 6, 2025 to cancel the December 2024 approval of Lava Ridge, which Interior described as a 1,000 MW project with up to 231 turbines. Construction of SWIP-N went ahead anyway. Idaho Power's block runs south to north only; its page says plainly that its ownership "only allows us to import energy." And PUC staff based its support on Idaho winter capacity, not on exports.

Where the evidence points: the line's CAISO majority was justified by California's interest in Idaho wind, and that block can carry power south whatever Idaho Power does. Idaho Power's block was justified by Idaho winter imports. Interior's move to cancel Lava Ridge removed the best-known wind project but not the CAISO portfolio assumption, and not the line's ability to serve some future project. Watch CAISO's planning documents and CPUC portfolios for whether Idaho wind stays in them.

One more piece of the deal matters here. The Department of Energy agreed to "initially hold and fund 22.831%" of the line as a backstop, up to $331 million, in case Idaho Power didn't commit or didn't win PUC approval. That block was the 500 MW running south to north, the same block Idaho Power now holds, and CAISO's filing said DOE meant to sell it to a utility. It carries imports into Idaho. FERC's January 21, 2025 order describes the whole line as "approximately 2,000 MW of firm, bidirectional transmission capacity from Idaho to the CAISO region," and allocated about $950 million of cost to CAISO ratepayers. Nobody protested.

What the developer's own consultants wrote

CAISO's memo isn't the only document tying the line to Idaho wind. Two studies by the Brattle Group, paid for by Great Basin, say it more plainly. Brattle's February 2021 benefits analysis, which measured benefits to CAISO only (up to $1.7 billion present value, against a $720 million revenue requirement), called SWIP-N "the final link of a transmission project that would create 1,000 MW of firm transmission rights from Idaho to California for CAISO." Its independent market report for Great Basin's DOE application priced Idaho wind delivered to CAISO at $40 per MWh: $34 for the wind farm and $6 for SWIP-N capacity. LS Power's April 2022 "Nevada Transmission Overview" put the corridor at about 2,100 MW, with about 1,000 MW reserved by NV Energy and LS Power "entitled to ~1100 MW from Midpoint to Harry Allen," the path toward California.

Jeff Pierson's Idaho Power / SWIP-N Point by Point Rebuttal and Part 2 (November 2025) set those documents beside Idaho Power's public line that its ownership interest is "only to bring energy into Idaho, not to sell energy to California or elsewhere." Use them as a model of the method: quote the utility's claim, then quote the filing. Idaho Power's contract rights do run north. The rest of the line was financed on power moving south. Both are true at once, and readers deserve both.

Example: holding a utility to its own planning record

  • Idaho Power's SWIP-North page calls the project "a critical piece of our ability" to deliver affordable energy.
  • Its 2023 Integrated Resource Plan, acknowledged by the PUC in case IPC-E-23-23, said "Idaho Power's potential involvement in the project remains uncertain and, therefore, the SWIP-N project is not included in the Preferred Portfolio of this IRP."
  • The PUC acknowledged that plan in Order No. 36233 on June 18, 2024, and staff asked for "more detailed information about the scope and cost of the SWIP-N project."
  • The 2025 IRP put SWIP-N in the preferred portfolio, online November 2028. The PUC acknowledged it in Order No. 36937 on February 17, 2026. So the accurate sentence is "Idaho Power changed its plan in 2025," and the reporting question is what changed. The plan cites nearly 1,000 MW of new peak load in five years; Idaho Capital Sun tied much of it to Micron's Boise expansion and a Meta data center in Kuna.
  • Rule: date every quote from a utility plan. The plans are rewritten every two years.

Common mix-ups

  • Claim: Idaho Power owns most of SWIP-N. What the evidence shows: It owns about 11.4 percent and holds rights to another 250 MW. CAISO's block is 77 percent.
  • Claim: SWIP-N died with Lava Ridge. What the evidence shows: Construction began in summer 2026.
  • Claim: SWIP-N dodged interregional review. What the evidence shows: It went through interregional evaluation in 2016-2017 and 2018-2019 and wasn't selected there. CAISO then approved it as a regional policy-driven project. Under FERC Order 1000, each planning region judges an interregional project under its own process; there is no joint approval by state utility commissions.
  • Claim: SWIP-N is a merchant line that earns no regulated return. What the evidence shows: Great Basin recovers costs through a FERC-accepted cost-based formula rate, effective August 20, 2025.
  • Claim: DOE called it a "$1+ billion, 285-mile" line. What the evidence shows: That wording is from LS Power's April 25, 2024 press release. Credit the company.
  • Claim: Idaho customers pay for the whole line. What the evidence shows: The CAISO block's costs go through CAISO's transmission rates. Idaho customers face only Idaho Power's share, after a future PUC case.

Reporting angle

  • Watch case IPC-E-25-08 and any new Idaho Power case for SWIP-N cost recovery. Compare the requested amount with the proportional bracket above.
  • Ask Idaho Power and Great Basin to reconcile the in-service dates: the developer says 2028, the 2025 IRP says November 2028, and Idaho Power's page has said 2029.
  • Check whether the DOE capacity contract was signed and what share of capacity it covers. Ask DOE's Grid Deployment Office directly; file a FOIA request under 5 U.S.C. 552 for the contract if it is not posted.
  • Follow CAISO's annual transmission plan and the CPUC's portfolio decision for Idaho wind assumptions.
  • Read FERC's two fall 2025 orders in eLibrary. The October 31 order (193 FERC ¶ 61,083, docket ER25-2025) accepted Great Basin's transmission tariff and formula rate, granted abandoned-plant and regulatory-asset incentives, and conditionally granted Great Basin a 50-basis-point return adder for joining CAISO, effective only once it turns over operational control. Great Basin's study claimed $38.6 million a year in congestion savings, mostly on the California-Oregon Intertie; CAISO's own estimate was $23.8 million. The November 4 order (193 FERC ¶ 61,094, dockets ER25-3372 and ER25-3376) accepted the Participation and Joint Ownership Agreement effective November 5, 2025. It declined to decide whether GBT Northbound is a public utility or whether Idaho Power and LS Power are affiliates, "without prejudice" to a later petition. It granted the Minidoka Pilgrimage Planning Committee intervention and denied its protest; NV Energy, California's Department of Water Resources, NCPA and Stop Lava Ridge also intervened. Pierson's Who Owns the Future of Power in Idaho? covers the November order. Note the adder is Great Basin's, in CAISO rates; Idaho customers pay only what the Idaho PUC allows for Idaho Power's share.
  • Numbers to check: final installed cost, Idaho Power's owned share, annual capacity fees for the leased 250 MW, and actual winter imports once energized.

Research angle

Check yourself

1. What share of SWIP-N does CAISO fund, according to its September 2024 board memo?

2. In the Idaho PUC certificate case, which party recommended denial?

3. What capacity deficits did PUC staff say Idaho Power faces without SWIP-N?

4. What did CAISO's 2024 memo say about the California rationale for SWIP-N?

5. When did SWIP-N construction begin, according to the developer's September 2026 announcement?

6. How many public comments did the PUC record in the SWIP-N case?

Terms in this lesson

SWIP-N
Southwest Intertie Project-North, a 285-mile, 500 kV line from Midpoint substation in south central Idaho to Robinson Summit substation near Ely, Nevada.
Capacity entitlement
The right to schedule a set number of megawatts in a given direction on a line.
Transmission Facilitation Program
A U.S. Department of Energy program that can act as an early capacity buyer on large new lines to help them get financed.
Anchor tenant
The big, committed buyer of a project's capacity whose contract makes financing possible.
Indefeasible entitlement
A capacity right that cannot be taken away; Idaho Power's certificate covers one for 250 MW northbound.

Full glossary

Sources