Western Transmission Megaproject: Who Pays for Idaho's Winter Power Import?

LS Power, through its affiliate Great Basin Transmission, has begun construction on the Southwest Intertie Project-North (SWIP-North), a 285-mile, 500-kilovolt transmission line connecting the Midpoint Substation near Twin Falls, Idaho, to the Robinson Summit Substation near Ely, Nevada, with an expected 2028 in-service date and a cost exceeding $1 billion^[1][2]. The project is framed as essential infrastructure to strengthen grid reliability and reduce congestion in the western United States, but a closer look at how the need was justified and who will bear the costs reveals the mechanism by which transmission capital gets built first and alternatives get studied never.

Start with need. Idaho Power describes SWIP-North's primary benefit as importing lower-cost winter power to heat Idaho homes and businesses, a seasonal arbitrage play that is economically coherent but historically contingent^[3]. The California Independent System Operator (CAISO) selected Great Basin Transmission to develop and finance the line in 2023, and CAISO provided final approval in 2024^[7]. Neither the public record of those approvals, nor Idaho Power's planning documents, nor the news releases state whether the utility conducted a mandatory grid-enhancement-technologies (GETs) screen before advancing a $1 billion capital project. Did the owner evaluate dynamic line ratings on existing corridors, advanced power-flow control, or storage-as-transmission as a congestion relief alternative? The regulatory regime creates no incentive to say yes: a transmission owner earning a FERC-regulated return on capex has no profit motive to choose a cheaper non-wires solution, and GETs-first review exists in some RTOs precisely to supply the incentive the rate-base structure removed. In the West, that scrutiny depends on whether the regional planning process was invoked at all, and public access to that analysis is thin.

Next, cost allocation. SWIP-North is a bi-directional line capable of moving more than 2,000 megawatts of electricity^[7], but Idaho Power has contracted only to use it for import, with capacity of up to 500 megawatts to its own customers^[3]. That means the Western grid is underwriting capital and ongoing transmission costs for a facility whose primary user is one utility, while the broader benefits (congestion relief, interregional connectivity) are claimed but not priced or tracked. FERC Order 1920, adopted in May 2024, requires long-term regional planning and forces regions to allocate interregional transmission costs by reference to an enumerated list of benefits (production-cost savings, reliability, resilience, avoided-cost, capacity), with a six-month state engagement period and filed backstop methods. The compliance filings through 2025 and 2026 will show how the Western grid actually answers the question: who benefits enough to pay? If Idaho Power and other regional beneficiaries are scored narrowly (import value to Idaho only), then the broader public and other western utilities subsidize the line's carrying costs. If benefits are scored broadly (grid-wide congestion relief), then the cost-allocation logic must be transparent and auditable, with explicit benefit calculations per party. Public comment on those compliance dockets is where to watch.

The deeper structural problem is that SWIP-North, like most Western transmission, was not developed through the competitive-bidding regime that FERC Order 1000 created in 2010. CAISO selected the builder directly, meaning there is no public price discovery showing what an independent competitor would have bid to build this line, finance it, or operate it. In MISO, SPP, and NYISO, competitively bid transmission projects have repeatedly come in 20 to 40 percent below incumbent cost-plus estimates, according to analyses by Brattle Group and others. The West's architecture does not mandate competitive solicitation for interregional projects, leaving LS Power and other incumbent transmission owners with pricing power that the broader grid cannot see and ratepayers cannot compare. Some states have enacted right-of-first-refusal (ROFR) statutes that explicitly prevent competitive bidding for new regional transmission; while the West has not adopted that model to the same degree as the Upper Midwest, the absence of a mandatory competitive process produces the same outcome: capital costs are whatever the builder bids, and the builder knows there is no alternative proposal on the table.

Idaho Power's customers will see the benefit if the seasonal arbitrage works as promised and if the cost allocation is fair. But neither of those is guaranteed by the regulatory structure. A concrete, buildable alternative exists: before any new $1 billion transmission line breaks ground in a western state, require the region to file a mandatory GETs-first screening in the RTO planning docket, with independent engineering review, cost-per-MW-relieved comparison against the capital project, and explicit cost-allocation methodology showing which utilities and which ratepayers bear each dollar. If SWIP-North clears that hurdle, open the project to competitive bidding and force the incumbent to bid against alternatives. The result would be lower capital cost, tighter project scope, and ratepayers bearing only the cost of benefits they actually receive.