Elmore County and the Rest of the Magic Valley

Elmore County has become one of the busiest energy dockets in southern Idaho without much attention from the rest of the state. It has Idaho Power's biggest proposed new plant, a new substation and lines, two solar permits, a combined wind, solar and storage application, an old pumped storage proposal, and the edge of a data center on federal land. The Magic Valley proper has its own list. This lesson takes them in turn.

Elmore County, as of October 2026

Project	What	Case	Status
Peregrine Power Plant	Idaho Power gas plant, 430 MW, an H-class simple-cycle combustion turbine on Simco Road between Mountain Home and Boise, with a 10-acre substation	PUC IPC-E-26-04; county CUP-2025-32, VAR-2026-05 and VAR-2026-06	County findings and orders on the April 30, 2026 P&Z consent agenda; PUC case open, no final order as of Sept. 25, 2026; target June 1, 2030
Mayfield Substation and transmission lines	Idaho Power facilities	CUP-2025-25	On the April 30, 2026 consent agenda
Soles Rest Solar	Up to 149 MWac on about 981 leased acres	CUP-2025-29	Staff recommended approval; workshop July 23, 2026
Crimson Orchard Solar and storage (Clenera)	100 MWac solar plus 100 MWac battery on Simplot land	CUP-2024-18	P&Z hearing March 13, 2025
Desert Ridge Winds	Utility-scale wind, solar and storage in eastern Elmore County	CUP-2024-01	Public workshop April 30, 2026; no hearing date found; size not found in county records reviewed
Rhea Data rights-of-way	Transmission and wiring for a data center on BLM land in southern Ada County	BLM Four Rivers Field Office	Pre-planning; notice of intent planned before end of 2026
Cat Creek Energy	Pumped storage between a planned 1,900-acre Cat Creek Reservoir and Anderson Ranch Reservoir, about 480 acres of solar, up to 39 wind turbines up to 510 feet tall	FERC licensing	In June 2022 FERC required a more in-depth licensing process; current status not confirmed for this course

The Idaho Department of Lands also sought wind or solar lease proposals on more than 6,000 acres of state endowment land in Elmore County in 2020. Whether a lease resulted is something to ask the department.

The gas plants: Peregrine and South Hills

On March 11, 2026, Idaho Power asked the PUC for certificates to build two gas plants, case IPC-E-26-04. South Hills in Twin Falls County would provide up to 222 MW from twelve reciprocating engines, starting June 1, 2029, on a 20-acre parcel near the Milner hydro project. Peregrine in Elmore County would provide 430 MW from a simple-cycle combustion turbine, starting June 1, 2030. The company says they are the cheapest, least risky way to cover capacity deficits starting in 2029, and especially useful at winter peaks when solar and batteries do less.

The case is proceeding by modified procedure, meaning written comments instead of a hearing. Public comments were due July 31, 2026, and Idaho Power's reply August 14. Intervenors are the Idaho Irrigation Pumpers Association, which also petitioned for intervenor funding on August 28; Micron; and the Northwest Energy Coalition with Renewable Northwest. Idaho Power did not ask for binding ratemaking treatment; it says it will make a future filing for cost recovery, so no rate change is decided in this case.

For context, Idaho Power reported that hydropower supplied nearly 37 percent of its 2025 energy and natural gas 22.6 percent, with solar at 9.1 percent. Two of the four Jim Bridger units in Wyoming were converted from coal to gas in early 2024, the North Valmy plant in Nevada is converting too, and the 2025 IRP plans 611 MW of coal-to-gas conversions in all.

The accounting order nobody reads

The same case asks the PUC to confirm that Idaho Power may accrue Allowance for Funds Used During Construction on both plants, starting with initial procurement. AFUDC is the financing cost of money tied up in a plant before it runs. It gets added to the plant's value, and if the plant is later found prudent, customers pay it back over the plant's life along with a return.

The rest of the Magic Valley

Project	Where	Size	Status
South Hills Power Plant	Twin Falls County	222 MW gas	PUC IPC-E-26-04 open; target June 1, 2029
Taurus Wind (Arevia Power)	BLM land, Gooding, Lincoln and a neighboring county	500 MW on about 49,194 acres	BLM forum Jan. 28, 2025; no later decision found
Snake River Energy Solar (Arevia Power)	Same area	400 MW on about 4,609 acres, with 550 MW of shared storage	Same
Salmon Falls Wind (Magic Valley Energy)	BLM land, Twin Falls County	About 800 MW	Announced March 2022; a tracker lists its Rogerson queue request as suspended
Snake River Energy Data Center (Copia)	BLM land north of Twin Falls	Not stated	Beginning environmental review, per September 2026 reporting
SWIP-N	Midpoint Substation to Nevada	500 kV, 285 miles	Under construction; service expected 2028

The pattern across both tables: federal land carries the biggest proposals, and their fate depends on federal policy. Private land carries the projects that are actually moving, through county permits and the PUC. Gas is advancing fastest because the utility is the applicant and the regulator has a capacity deficit in front of it.

The arguments on the gas plants

Idaho Power and its supporters argue the plants are the least-cost, least-risk answer to a documented deficit, and that gas covers winter peaks that solar and batteries cannot. Conservation intervenors argue for more storage, demand response and efficiency first, and for scrutiny of fuel price risk and emissions. Irrigators, who pay heavy demand charges, are watching how much of the cost lands on them. Jeff Pierson's view, laid out across Feeding the Beast, is that the growth driving the deficit comes largely from large new loads, and that existing customers should not pay to build for them. IPC-E-26-04 does not settle that question. The large-load cost case, IPC-E-26-07, and the 2026 law requiring new loads of 50 MW or more to pay full cost of service, Idaho Code 61-335, are where it gets decided.