Idaho HVAC Load Calculation Guide
Idaho's Snake River Plain stretches from Boise's hot-dry summers to Idaho Falls' -11°F winters — two climates that require very different HVAC strategies within the same state, compounded by Boise's position as one of the fastest-growing US metros.
Try the Idaho HVAC Load Calculator
Get a preliminary estimate using Idaho-specific design temperatures. Our heating load calculator uses ASHRAE methodology with the local climate inputs below.
Design Temperatures
| Parameter | Value | Source |
|---|---|---|
| Winter Design Temperature (99%) | -11°F | ASHRAE Handbook 2021 |
| Summer Design Temperature (1%) | 99°F | ASHRAE Handbook 2021 |
| IECC Climate Zone(s) | 5B (Cool - Dry), 6B (Cold - Dry) | ASHRAE 169-2021 |
| HVAC Load Type | Heating-Dominated | — |
Idaho Building Codes & Energy Requirements
| Requirement | Detail |
|---|---|
| Energy Code | Idaho Energy Conservation Code (2018 IECC, statewide since 2020) |
| Minimum SEER | 14.0 SEER (federal minimum) |
| HVAC License Required | Yes — Idaho Division of Building Safety — Mechanical Contractor license required |
| Average Electricity Rate | $11.0/kWh (US average: $0.1701/kWh) |
Major Cities — Design Temperature Reference
| City | Summer Design (1% DB) | Winter Design (99% DB) | Load Type |
|---|---|---|---|
| Boise | 99°F | -11°F | Heating |
| Nampa | 99°F | -11°F | Heating |
| Meridian | 99°F | -11°F | Heating |
| Idaho Falls | 94°F | -11°F | Heating |
| Pocatello | 95°F | -11°F | Heating |
Quick Facts
- State: Idaho (ID)
- Climate Zone(s): 5B, 6B
- Winter Design: -11°F
- Summer Design: 99°F
- Energy Code: Idaho Energy Conservation Code (2018 IEC...
- Avg. Electric Rate: $11.0/kWh
- License Required: Yes
Idaho HVAC Challenges
- Eastern Idaho (Idaho Falls/Pocatello) reaches -11°F winter design temperature near Yellowstone
- Boise's rapid growth in the Treasure Valley is driving new construction HVAC demand at high volume
- Potato and agricultural storage facilities require precise humidity and temperature control year-round
- Geothermal district heating in Boise — one of the largest US systems — affects mechanical design
- Snake River Plain wide temperature swings from hot dry summers to cold winters
- Silver Valley (Coeur d'Alene area) mining legacy creates specialized industrial HVAC contexts
Local Utilities & Resources
- Idaho Power (investor-owned)
- Avista Utilities (investor-owned)
- Rocky Mountain Power (investor-owned)
Idaho HVAC FAQ
The ASHRAE winter design temperature for Idaho is -11°F and the summer design temperature is 99°F. These values are used for heating and cooling load calculations per ACCA Manual J methodology.
Idaho spans 5B, 6B per ASHRAE Standard 169-2021. This classification determines minimum insulation requirements, energy code compliance path, and HVAC equipment sizing parameters.
The required HVAC size depends on home square footage, insulation levels, window area, and orientation. For a typical 2,000 sq ft home in Idaho, use our heating load calculator with the local design temperature of -11°F (winter) or 99°F (summer) for a preliminary estimate.
Idaho Division of Building Safety — Mechanical Contractor license required
Idaho follows the Idaho Energy Conservation Code (2018 IECC, statewide since 2020). This code sets minimum requirements for HVAC equipment efficiency, duct insulation, envelope insulation, and ventilation.
Design Guides & Standards for Idaho
Explore related resources for accurate HVAC sizing.