Idaho natural gas case study, Boise, Idaho. October 2026

Boise-area natural gas capacity: no area deficit in the utility's plan, but a company-wide supply shortfall from 2026

Intermountain told the Idaho Public Utilities Commission in December 2025 that it projects no peak-day deficit in its Canyon County and Central Ada County areas in any growth scenario through 2030, and that its State Street Lateral, which serves north Boise, Eagle, Meridian and Star, needs a capacity enhancement by 2026, which it has budgeted for 2026. For its whole system, Intermountain projects a peak-day deficit of 2,258 Dth in 2026 and 40,167 Dth in 2030 in its base case, and the Commission acknowledged the plan in July 2026 without approving any project.

0 DthProjected peak-day deficit, Canyon County and Central Ada County areas, all scenarios (utility projection)
2,258 DthIntermountain's projected 2026 peak-day deficit for its whole system, base case; system context
40,167 DthThe same whole-system deficit in 2030, base case; system context
950,000 therms per dayState Street Lateral capacity after the Phase II uprate budgeted for 2026, per Intermountain

By Sam Strong, Vice President of Business Development, Discovery Energy. Technical review by Tara Dugger, Chief Operating Officer. Updated .

Metro used: the Boise City, ID metropolitan statistical area, as delineated in OMB Bulletin No. 23-01 (July 21, 2023): Ada, Boise, Canyon, Gem and Owyhee counties. One gas distribution utility is identified in the record, Intermountain Gas Company (Intermountain). Its 2025 Integrated Resource Plan gives capacity tables for areas inside the metro (Canyon County, Central Ada County and the State Street Lateral) and a Total Company table for its whole Idaho system, so the company-wide figures below are labeled system context.6

Key takeaways

  • Intermountain said in its December 2025 plan that forecast peak-day use in its Canyon County Area stays within the area's 139,000 Dth maximum physical deliverability, and in its Central Ada County Area within 87,000 Dth, in all three growth scenarios, with no peak-day deficit projected through 2030.1
  • Intermountain said its State Street Lateral, which serves north Boise, Eagle, Meridian and Star, requires a capacity enhancement by 2026, and that the Phase II uprate budgeted for 2026 would bring lateral capacity to 950,000 therms per day, enough for predicted growth through 2030.3
  • System context: Intermountain's Total Company table, a whole-system figure not allocated to the Boise metro, shows a base-case peak-day deficit of 2,258 Dth in 2026 and 40,167 Dth in 2030 under existing resources.2
  • System context: Intermountain said the whole-system shortfall begins in 2026, attributed it to expiring contracts and growth, and said it selected the Rockies expansion by Northwest Pipeline while its Gas Supply Oversight Committee makes the final decision; the plan gives no in-service date.4
  • The Commission acknowledged the plan in an order served in July 2026, saying it did not approve the plan or any resource acquisition in it and did not allow any form of cost recovery.5
  • Intermountain's tariff curtails firm service in inverse order of four priorities set by daily therm volume and use, with firm requirements under 500 therms per day curtailed last, and its interruptible transportation service carries no assurance of distribution capacity on any given day.9

Which parts of the record fall inside the Boise metro?

Intermountain's plan divides its system into areas of interest. Three of them are inside the metro: the Canyon County Area, the Central Ada County Area, and the State Street Lateral, which begins in Middleton and serves the towns of Star, north Meridian, Eagle and northern Boise, towns in Canyon and Ada counties. System context: two are outside the metro, the Sun Valley Lateral, serving Blaine and Lincoln counties, and the Idaho Falls Lateral in eastern Idaho. Gem and Owyhee counties, which are in the metro, are covered only by an "all other" segment for which the plan gives no area deficit table.6

Where Item in Intermountain's plan
Inside the metro Canyon County Area; Central Ada County Area; State Street Lateral
Outside the metro, system context Sun Valley Lateral; Idaho Falls Lateral; Total Company deficit and upstream shortfall
Unclear Gem and Owyhee counties (no area table)

Intermountain's areas of interest and Total Company study, by whether they fall inside the Boise metro (OMB delineation). Sources: 2025 Integrated Resource Plan, Section 2.1 and Section 4.4.4.6

System context: the Total Company figures cover every Intermountain customer in Idaho. The record does not allocate them to the five metro counties.

How much spare gas capacity does Boise have on the coldest day?

Major natural gas pipelines serving Boise N Northwest Pipeline Northwest Pipeline Other transmission pipelines in the EIA layer (interstate and intrastate; unlabeled) Pipeline named in a verified claim on this page (labeled, one color each) Metro counties (boundary used on this page) Major highways (for orientation)
Figure 1. Major natural gas pipelines serving Boise. Simplified, not to scale. Discovery Energy illustration from EIA and U.S. Census data. Coastline, lakes and highways: Natural Earth (public domain).

Intermountain compared forecast peak-day use under design weather with each area's maximum physical deliverability. It reported no deficit under existing resources in the Canyon County Area (139,000 Dth) or the Central Ada County Area (87,000 Dth) in its low, base or high growth scenarios, 2025 to 2030, and no deficit on the State Street Lateral (95,000 Dth) because of planned upgrades.1

The one deficit is in the Total Company study, which Intermountain described as the volume of gas deliverable to it through available interstate resources, not the capacity of any lateral or area.2

Growth scenario 2025 2026 2027 2028 2029 2030
Low 0 0 5,462 11,404 17,858 24,175
Base 0 2,258 11,194 20,466 30,351 40,167
High 0 4,758 16,962 29,642 43,090 56,640

Intermountain's Total Company peak-day deficit under existing resources, design weather, in Dth, whole system (system context). Source: 2025 Integrated Resource Plan, Table 28.2

Intermountain said its Figure 64 "shows the shortfall created by expiring contracts" and attributed the shortfall also to growth in design capacity; it does not name which contracts expire or when.24

What is driving new natural gas demand?

Intermountain forecasts large growth in its large-volume manufacturing segment, 47% over the forecast period, which it attributes to a massive plant expansion already in process at one customer. The plan does not name the customer, its location or a service date, so the record does not show whether the load is in the Boise metro.7

A search of other official records found no further documented gas load in the five metro counties: EIA's September 2026 generator inventory lists no planned natural gas-fired generator there, and a search of Federal Register notices of the Federal Energy Regulatory Commission since January 1, 2025 found no pipeline notice naming any of the five counties.11 Intermountain attributes its need for added capacity to demand driven by population and economic growth, and its May 2026 release names no data center, power plant or other large load.12

Are upgrades arriving in time?

For the metro, Intermountain's plan shows these remedies. For the State Street Lateral, the need and the fix carry the same year: the plan says a capacity enhancement is required by 2026 and that the Phase II uprate is budgeted for 2026. For the Canyon County and Central Ada County areas, it says no reinforcements are needed to meet 2030 growth after recent investment, including the South Boise Loop and Kuna Gate upgrade completed in 2023.3

System context: for the whole-system shortfall, Intermountain said it selected the Rockies expansion proposed by Northwest Pipeline and also said its Gas Supply Oversight Committee will make the final decision on the solution; satellite liquefied natural gas is the other option named. The plan gives no in-service date.4

System context, since the plan: Intermountain said on May 11, 2026 that it signed a precedent agreement to contract 100,000 Dth per day of capacity on the proposed Rockies Columbia Connector pipeline, which it anticipates in service early in 2030. Williams, the owner of Northwest Pipeline, describes Silver Spur, the first phase of that concept, as adding 275 million cubic feet per day with an in-service target of early 2030. These are company statements; a precedent agreement is not an approved or built project, the record read contains no Commission approval of it, and the first year of the Total Company deficit in the plan is 2026.12

The Commission did not approve the plan or any resource acquisition in it.5

What does this mean for business gas costs?

The record gives no dollar or bill figure for capacity costs by customer class, so none is given here. These are the positions and rules on file:

  • In its general rate case, the Commission approved a settlement that raised Intermountain's authorized revenue requirement by $13 million, about 10.4% of margin revenue, with new rates effective January 2026.8
  • The Alliance of Western Energy Consumers said the settlement's rate spread acknowledges that large-volume sales and transportation customers pay rates in excess of their class cost of service; this is a party's position as recounted in the order, not a Commission finding.8
  • In its order acknowledging the 2025 plan, the Commission allowed no cost recovery and said the prudence of Intermountain's resource decisions is for a general rate case or other rate proceeding.5

Who bears the cost of any future capacity addition is not decided in this record.

Who gets gas first in a shortage?

Intermountain's tariff provides that curtailment of firm service is imposed in inverse order of four priorities, starting with the lowest-priority category, all other contracted customer uses, then firm commercial and industrial requirements of 2,000 therms or more per day, then requirements of 500 to under 2,000 therms per day, and ending with firm requirements of less than 500 therms per day. Within a priority, 100% of each customer's requirements is curtailed before the next priority.9

Interruptible transportation customers (rate schedule T-3) agree to curtail or interrupt operations immediately, if the company asks, during capacity constraints on its distribution system. Intermountain said it makes no assurance of capacity for T-3 service on any given day, and that for peak-event modeling its plan assumes T-3 customers are reduced to minimal emergency plant-heat only.9

Winter and market context

Context only, as of October 2026. It does not set the outlook level and makes no prediction of outages. Its sources are listed separately under Market and weather sources and are refreshed on the publication date.

NOAA's Climate Prediction Center said on October 15, 2026 that its November 2026 to January 2027 temperature outlook favors above-normal temperatures for, among other areas, the western third of the contiguous U.S., a discussion that names regions and not Idaho counties, and that the probability of at least a strong El Nino continuing through January to March 2027 is 80%.B1 The U.S. Energy Information Administration (EIA) said on October 6, 2026 that it expects U.S. natural gas inventories to enter the winter heating season 2% above the previous five-year average, and that prolonged periods of cold weather could increase withdrawals beyond its forecast.A1A2 EIA lists U.S. liquefied natural gas gross exports of 15 billion cubic feet per day in 2025, 18 in 2026 and 19 in 2027.A1 These are national and regional facts, not statements about the utility's system, and none of them is used to set the outlook on this page.

What is the outlook for Boise gas capacity through 2029?

Discovery Energy rates the outlook for Boise-area natural gas capacity through 2029 as Watch (confidence: Medium): Intermountain's own tables show no peak-day deficit in the Canyon County and Central Ada County areas, and the State Street Lateral's capacity need in 2026 has a scheduled fix budgeted for 2026, though the Commission approved no project; the company-wide shortfall is system context and is not counted in this level. Documented risk factors: none beyond the base level. Three developments would change the assessment: Intermountain's Gas Supply Oversight Committee decision on transportation for the whole-system shortfall, with an in-service date (Intermountain said in May 2026 that it anticipates early 2030 for the Rockies Columbia Connector); completion of the State Street Phase II uprate in 2026; the Total Company deficit table in Intermountain's next plan or any rate proceeding on the cost of capacity projects.

Outlook levels, from least to most concern: Stable, Watch, Elevated, High, Severe. Levels describe the public record of capacity and supply risk; confidence is reported separately. They are qualitative assessments, not forecasts of outages.

What should Boise-area facilities check now?

  • Tariffs and charges, through a utility audit. Confirm each account is on the right rate class and tariff, and that riders, demand charges and capacity-related charges are billed correctly. Over 70% of the clients Discovery Energy has audited were billed incorrectly. An audit verifies tariffs and charges and recovers overcharges before winter costs rise.
  • Which service, and which curtailment priority. Confirm whether each site is a firm or interruptible account, and where its daily therm volume places it among the four priorities in the tariff.
  • Interruptible terms. If a site takes service under rate schedule T-3, know that Intermountain makes no assurance of capacity on any given day.
  • Backup plans and fuel. Check that alternate-fuel and curtailment plans are current and feasible, and that fuel inventories and resupply arrangements are in place before December.
  • Upcoming proceedings. Track Intermountain's decision on transportation for the whole-system shortfall, the State Street uprate in 2026, and its next integrated resource plan.

Frequently asked questions

Will Boise businesses face natural gas shortages this winter?

The record does not show a shortage. Intermountain said in December 2025 that it projects no peak-day deficit in its Canyon County and Central Ada County areas through 2030, and a whole-system deficit of 2,258 Dth in 2026 in its base case, a figure for its whole Idaho system. This page makes no prediction about outages.

Is there spare gas capacity in the Boise area on the coldest day?

Intermountain reported no peak-day deficit under existing resources in the Canyon County Area (139,000 Dth maximum physical deliverability) or the Central Ada County Area (87,000 Dth), and none on the State Street Lateral because of planned upgrades. These are utility projections, not Commission findings.

What is the whole-system shortfall at Intermountain Gas?

Intermountain's Total Company table shows a base-case peak-day deficit of 2,258 Dth in 2026 and 40,167 Dth in 2030 under existing resources, for its whole system. It attributed the shortfall to expiring contracts and growth, and said its Gas Supply Oversight Committee will decide the solution.

Did the Commission approve Intermountain's plan?

The Commission acknowledged the plan in July 2026, saying it did not approve the plan or any resource acquisition in it, and allowed no cost recovery.

Who is cut first if Intermountain must curtail service?

Under its tariff, firm service is curtailed in inverse order of four priorities, and firm requirements under 500 therms per day are curtailed last. Interruptible transportation customers under rate schedule T-3 agree to curtail when the company asks.

Is a data center driving gas demand in Boise?

The record does not show one. Intermountain's plan cites a large plant expansion at one unnamed manufacturing customer, with no location or service date. A search of EIA's September 2026 generator inventory and of Federal Energy Regulatory Commission pipeline notices found no planned gas-fired generator or pipeline project naming the five metro counties.

Related case studies

Discovery Energy publishes gas capacity case studies for other metros, using the same method and outlook scale.

Understand your capacity exposure

Discovery Energy reviews service elections, interruption terms and regulatory proceedings for organizations across the US and Canada, so capacity changes are understood before they reach the bill.

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Notes

  1. Intermountain Gas Company, 2025 Integrated Resource Plan (filed December 23, 2025; Idaho PUC Case INT-G-25-08), Section 4.4.4, PDF 121 (Tables 23 and 24) and PDF 123 (Table 27). Utility statements. [BOI-01 to BOI-05] ↩
  2. Same plan, PDF 123 (Table 28, Total Company) and PDF 162. First year with a deficit by scenario, run by code (boise_calculations.csv): low 2027, base 2026, high 2026; illustrative. [BOI-07 to BOI-12] ↩
  3. Same plan, Section 4.3: PDF 105 (Canyon County), PDF 106 (Central Ada County, State Street Lateral) and PDF 107 (State Street Phase II uprate). [BOI-06, BOI-15 to BOI-18] ↩
  4. Same plan, Section 4.6.3, PDF 162 and PDF 163. [BOI-11 to BOI-14] ↩
  5. Idaho Public Utilities Commission, Final Order No. 37108, Case INT-G-25-08, service date July 27, 2026, PDF 4. Commission order. [BOI-22, BOI-23] ↩
  6. Same plan, PDF 19 and PDF 106; metro counties from metro_counties.csv; classification in boise_metro_classification.csv. The match of towns to counties is general geography, not a quotation. [BOI-24 to BOI-26] ↩
  7. Same plan, Section 2.4, PDF 47. [BOI-19] ↩
  8. Idaho Public Utilities Commission, Final Order No. 36889, Case INT-G-25-02, service date December 30, 2025, PDF 2, 3 and 6. The Alliance of Western Energy Consumers' position is as recounted in the order. [BOI-27 to BOI-29] ↩
  9. Intermountain Gas Company tariff on file with the Commission: General Service Provisions, Section A, paragraph 16 (curtailment, sheet effective October 2020), PDF 36, and rate schedule T-3 (sheet effective January 2026), PDF 15; and the 2025 plan, Section 2.4.4, PDF 42. Tariff sheets may have been revised since; check the current approved sheets before relying on them. [BOI-20, BOI-21, BOI-30 to BOI-34] ↩
  10. Not established, and left out of the page: supply events since 2020 affecting Intermountain (the plan names only the 2018 Enbridge pipeline rupture, outside the window; pipeline critical notices and the weekly storage archive were not searched); delivery-point utilization from pipeline postings (not captured; next capture about March 2027); how any capacity project would be allocated among customer classes; the Commission Staff comments in the plan review (not downloaded); the in-service date of the Rockies expansion.
  11. EIA-860M inventory for September 2026 (Planned sheet, operator-reported planned dates), filtered to Ada, Boise, Canyon, Gem and Owyhee counties by code, and a Federal Register search of FERC notices since January 1, 2025 by county phrase, both computed by code (boise_calculations.csv). A notice that spells a place differently would be missed. [BOI-35, BOI-36] ↩
  12. Intermountain Gas Company, news release, May 11, 2026 (precedent agreement on the proposed Rockies Columbia Connector); Williams, Q1 Earnings Recap, May 5, 2026 (Silver Spur). Company statements, saved October 25, 2026; Williams's FERC filing for the project was not saved. [BOI-37, BOI-38, BOI-39, BOI-40, BOI-41] ↩
  13. R3 not established, and left out of the claims (searches run: EIA-860M, a Federal Register search of FERC notices by county, and utility and pipeline-company pages): state air permit records, FERC eLibrary filings, each utility's own large-load request list and county economic development filings, none of which a script could save; news reports are leads only and are not claimed. Idaho DEQ's public comment list, saved October 25, 2026, showed no gas-fired unit in the five counties, but DEQ's permit records were not searched by code. A draft permit revision for Idaho Power's Bennett Mountain Power Plant in Elmore County (outside the metro) appeared only in search results and was not read in a DEQ document, so it is not claimed. Idaho Power does not publish an interconnection queue in a form code could save.

Market and weather sources

Public web sources saved and hashed on October 25, 2026. They are context, separate from the regulatory record cited in the Notes. The Climate Prediction Center issues its seasonal outlook once each month near mid-month; this section is refreshed on the publication date.

  1. A1. U.S. Energy Information Administration, press release, "EIA expects a mixed picture for winter fuel costs this year," October 6, 2026. Link ↩
  2. A2. U.S. Energy Information Administration, Short-Term Energy Outlook, October 2026 (natural gas storage). Link ↩
  3. B1. NOAA Climate Prediction Center, Prognostic Discussion for Long-Lead Seasonal Outlooks, issued October 15, 2026. Link ↩

Sources

  1. Intermountain Gas Company, 2025 Integrated Resource Plan. Link
  2. Idaho Public Utilities Commission, Case INT-G-25-08, Final Order No. 37108. Link
  3. Idaho Public Utilities Commission, Case INT-G-25-02, Final Order No. 36889. Link
  4. Idaho Public Utilities Commission, Intermountain Gas Company gas tariff. Link
  5. Office of Management and Budget, OMB Bulletin No. 23-01, Revised Delineations of Metropolitan Statistical Areas, Micropolitan Statistical Areas, and Combined Statistical Areas, July 21, 2023.
  6. U.S. Energy Information Administration, EIA-860M Preliminary Monthly Electric Generator Inventory, September 2026. Link
  7. Federal Register, API search of Federal Energy Regulatory Commission notices by county. Link
  8. Intermountain Gas Company, news release, May 11, 2026. Link
  9. Williams, Q1 Earnings Recap, May 5, 2026. Link