Intermountain Gas Company Rate Selection Guide
Intermountain Gas Company is the primary natural gas distributor in Southern Idaho, serving roughly 350,000 customers across 75 communities as a subsidiary of MDU Resources Group. It is a regulated utility under the Idaho Public Utilities Commission, offering self-service billing data access and formal authorization processes for commercial and industrial customers.
Intermountain Gas Company Rate Schedule Comparison
| Schedule | Type | Rate | Best For |
|---|---|---|---|
| GS-1 | Commercial bundled | Per-therm tariff (Cost of Gas + Distribution); see GS-1 PDF | Small commercial / light industrial up to 2,000 therms/day |
| LV-1 | Industrial bundled | Bundled per-therm per LV-1 tariff/contract | Large facilities using 200,000-500,000 therms/year wanting full-service supply |
| T-4 | Firm transportation | MDFQ demand charge + volumetric transport per T-4 tariff | Large facilities (>=200,000 therms/yr) that procure their own gas and need firm delivery |
| T-3 | Interruptible transportation | Volumetric transport per T-3 tariff (no demand charge) | Large facilities able to tolerate curtailment in exchange for lower delivery cost |
Market Overview
Intermountain Gas is a regulated investor-owned natural gas distribution utility under the Idaho Public Utilities Commission. Most customers have no retail supplier choice and pay IPUC-approved bundled tariff rates. Large-volume industrial customers (>=200,000 therms/year) may elect transportation-only service and procure their own gas supply, paying Intermountain for distribution delivery only.
Need to pull your actual usage data to compare rates? See the Intermountain Gas Company Data Access Guide →
Current Rate Schedules
Intermountain Gas C&I rates are set by IPUC-approved tariffs. Each schedule's per-therm Cost of Gas, Distribution Cost, and Customer Charge are published in the individual rate schedule PDFs and trued-up periodically via the Purchased Gas Cost Adjustment (PGA). Per the October 1, 2025 PGA, commercial GS-1 customers saw a roughly 0.03% decrease, while large-volume LV-1 (+5.06%), T-3 interruptible transportation (+10.76%), and T-4 firm transportation (+11.30%) saw increases driven by higher gas commodity and pipeline transportation costs. Specific per-therm figures are itemized in the tariff schedules linked below.
Effective: January 1, 2026 · Full Tariff Book →
| Schedule | Type | Applicability | Structure | Rate |
|---|---|---|---|---|
| GS-1 General Service | commercial | Small commercial and light industrial customers whose requirements do not exceed 2,000 therms/day at any point on the distribution system. Requirements above 2,000 therms/day may be served under a one-year written contract. | Bundled volumetric rate (per-therm Cost of Gas + Distribution Cost) plus a fixed monthly Customer Charge and Energy Efficiency Charge. Per-therm rates set by IPUC tariff. | Per-therm rate published in GS-1 tariff schedule (Cost of Gas + Distribution Cost components); ~0.03% commercial decrease effective Oct 1, 2025 PGA.+ None for GS-1 |
| LV-1 Firm Sales (Large Volume Bundled) | industrial | Large-volume customers using at least 200,000 but not more than 500,000 therms/year at a single facility; requires a minimum one-year service contract. | Fully bundled sales tariff: Intermountain procures gas supply and combines it with firm distribution and firm interstate pipeline transportation capacity, managing daily and monthly balancing. Rates set by IPUC tariff/contract. | Bundled per-therm rate per LV-1 tariff and contract; approximately +5.06% effective Oct 1, 2025 PGA.+ Included in bundled service; reflects reserved firm capacity |
| T-4 Firm Distribution-Only Transportation | industrial | Large-volume customers using >=200,000 therms/year who procure their own gas supply and execute a service contract; firm delivery. | Transportation-only: customer buys and delivers its own gas to Intermountain at the Northwest Pipeline citygate; Intermountain redelivers on a firm basis. Contract sets a Maximum Daily Firm Quantity (MDFQ) used to calculate a monthly demand charge. | Distribution demand + volumetric transportation charge per T-4 tariff; approximately +11.30% effective Oct 1, 2025 PGA.+ Monthly demand charge based on MDFQ (reserved distribution capacity) |
| T-3 Interruptible Distribution Transportation | industrial | Large-volume customers using >=200,000 therms/year who procure their own gas supply; interruptible delivery subject to curtailment at Intermountain's discretion. | Transportation-only interruptible service: customer supplies its own gas; Intermountain redelivers on an interruptible basis with no firm capacity reservation. Rates set by T-3 tariff. | Volumetric interruptible transportation charge per T-3 tariff; approximately +10.76% effective Oct 1, 2025 PGA.+ None (interruptible, no firm capacity reservation) |
| IS-C Interruptible Snowmelt (Commercial) | commercial | Small commercial customers using natural gas to melt snow and/or ice on sidewalks, driveways, or similar appurtenances (separate meter required). | Interruptible volumetric rate for snowmelt usage; per-therm rate set by IPUC tariff. | Per-therm rate published in IS-C tariff schedule.+ None |
Rate Recommendations by Use Case
Small commercial facility (under 2,000 therms/day)
Stay on GS-1 General Service and access billing/usage data through the Online Account Services portal.
GS-1 is the default bundled commercial schedule; below 200,000 therms/year, large-volume tariffs are not available.
- Enable eBill and email alerts for monthly usage tracking
- Claim EE-GS efficiency rebates on qualifying equipment
- Use Multi-Account Access for multiple locations
Large facility wanting full-service supply (200k-500k therms/yr)
Use LV-1 Firm Sales for fully bundled gas supply, distribution, and balancing managed by Intermountain.
LV-1 suits high-volume facilities that prefer Intermountain to manage supply and daily/monthly balancing under a one-year contract.
- Execute the required one-year service contract
- Note the 500,000 therms/year upper bound for LV-1
- Compare bundled WACOG against self-supply under transportation tariffs
Large facility procuring its own gas with firm delivery
Choose T-4 Firm Distribution-Only Transportation and engage a marketer to manage supply, nominations, and balancing.
T-4 gives firm delivery up to the MDFQ while letting the customer capture commodity market pricing; best for facilities needing reliable supply.
- Set the MDFQ carefully - it drives the monthly demand charge
- Engage a marketer from Intermountain's marketer list
- Manage daily nominations within imbalance tolerances
Large facility with curtailable load seeking lowest delivery cost
Consider T-3 Interruptible Transportation to avoid the firm-capacity demand charge, accepting curtailment risk.
T-3 omits the MDFQ demand charge, lowering fixed delivery cost for facilities that can tolerate interruption (e.g., with backup fuel).
- Ensure backup fuel or curtailable processes are in place
- Engage a marketer for nominations and balancing
- Compare savings vs. T-4 firm-delivery reliability
Historical Rate Trends
Intermountain Gas rates are adjusted primarily through the annual Purchased Gas Cost Adjustment (PGA), which trues up the cost of gas, plus periodic general rate cases. The most recent PGA took effect October 1, 2025 (Case INT-G-25-04).
October 1, 2025
PGA (INT-G-25-04): T-4 firm transportation customers increase of approximately $435/month.
+11.30%October 1, 2025
PGA (INT-G-25-04): T-3 interruptible transportation customers increase of approximately $483/month.
+10.76%October 1, 2025
PGA (INT-G-25-04): LV-1 large-volume bundled customers increase of approximately $649/month.
+5.06%October 1, 2025
PGA (INT-G-25-04): Commercial (GS-1) customers slight decrease of about $0.06/month.
-0.03%Overall trend: Mixed by class: residential and commercial customers saw slight decreases in the Oct 2025 PGA, while large-volume and transportation customers saw notable increases driven by higher gas commodity and interstate pipeline transportation costs.
Next expected change: Next annual PGA expected around October 1, 2026; a separate general rate case (filed 2025) may also affect base distribution rates.
Cost Optimization Strategies
For C&I customers, the largest savings levers at Intermountain Gas are matching the rate schedule to annual volume and load profile, and deciding whether to self-supply gas under transportation tariffs.
Right-size the rate schedule by volume
For: C&I facilities near or above 200,000 therms/year
Facilities approaching or exceeding 200,000 therms/year should evaluate large-volume tariffs (LV-1, T-3, T-4) instead of remaining on GS-1, as large-volume rates and structures are generally more economical at high throughput.
Evaluate transportation vs. bundled service
For: Industrial customers >=200,000 therms/year with supply management capability
Large facilities that can engage a marketer to procure their own gas can move from LV-1 bundled service to T-4 firm or T-3 interruptible transportation, paying Intermountain for delivery only and capturing commodity market pricing.
Consider interruptible (T-3) for curtailable loads
For: Industrial customers with flexible/curtailable load
Facilities with backup fuel or curtailable processes can choose T-3 interruptible transportation to avoid the firm-capacity demand charge associated with T-4, lowering fixed delivery costs.
Use energy efficiency rebates (EE-GS)
For: Commercial customers on GS-1
GS-1 commercial customers can claim rebates under the General Service Energy Efficiency program toward qualified high-efficiency natural gas equipment.
To implement these strategies, you need your 15-minute interval data. Learn how to download Intermountain Gas Company interval data →
Frequently Asked Questions
How does a commercial or industrial customer access their billing and usage data from Intermountain Gas?▾
Through the Online Account Services portal at customer.intgas.com, which shows up to 24 months of monthly billing statements and usage history with year-over-year graphs. Multi-factor authentication is required. Customers with multiple facilities can manage all accounts under one login via Multi-Account Access.
Can a consultant or energy manager access a C&I customer's data on their behalf?▾
Yes. The customer completes either the Customer's Agent Authorization Form (broad account access) or the Consent to Disclose Utility Energy Usage Information Form (usage data only), available on the Customer Forms page, and submits it to customerservice@intgas.com. Note the Agent form is not available for interruptible or transportation rate customers. For aggregated/anonymized portfolio data, use the Energy Data Usage Request form.
Does Intermountain Gas provide interval data or Green Button access?▾
No. Intermountain uses AMR (Automated Meter Reading) meters that capture only monthly consumption totals, not 15-minute or hourly interval data. There is no Green Button (Download My Data or Connect My Data), ESPI API, or developer portal. Only monthly usage is available.
What rate schedules are available to industrial customers and how do I qualify?▾
Facilities using at least 200,000 therms/year at a single facility qualify for large-volume tariffs and must execute a one-year contract. Options are LV-1 (bundled sales, up to 500,000 therms/yr), T-4 (firm transportation-only with an MDFQ demand charge), and T-3 (interruptible transportation-only). Below that threshold, customers are served under GS-1 General Service.
How do Intermountain Gas C&I rates change over time?▾
Rates are adjusted mainly through the annual Purchased Gas Cost Adjustment (PGA) and periodic general rate cases approved by the Idaho PUC. In the October 1, 2025 PGA (Case INT-G-25-04), large-volume LV-1 rose about 5.06%, T-3 about 10.76%, and T-4 about 11.30%, while commercial GS-1 saw a slight decrease, driven by higher gas commodity and pipeline transportation costs.
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