Energy demand is growing fast across Idaho Power’s service area. To ensure our customers continue receiving the reliable, affordable energy they depend on, Idaho Power is proposing an expansion of the   Bennett Mountain Power Plant in Mountain Home. The expansion could power up to 60,000 homes when customers’ energy needs are at their highest — like hot summer and cold winter days.

The expansion would include nine units flexible enough to generate anywhere between 10 and 167 megawatts, providing a fast-ramping resource that doesn’t depend on weather like wind and solar power.

Why is Idaho Power considering this location?

Idaho Power can save money for its customers by expanding the Bennett Mountain Power Plant and using infrastructure that’s already in place, including a natural gas pipeline, substation, and transmission line.

What would this expansion look like?

The expansion would include nine generating units. Each unit would have an exhaust stack that measures up to 90 feet high.

Safety

The Bennett Mountain Power Plant has operated safely throughout its 20-year history. This plant is maintained by qualified Idaho Power employees trained in the safe operation of natural gas power plants. Idaho Power is working with the Mountain Home Fire Department and Elmore County Rescue to ensure a strong emergency response strategy for this proposed expanded facility.

Emissions

The expansion would comply with all local and national air quality standards. The Idaho Department of Environmental Quality must approve a Permit to Construct before the expansion is built. Idaho Power plans to apply for this permit by the end of August 2025 and expects to receive it by fall 2026.

Sound

The Bennett Mountain Power Plant has been in operation for 20 years without any sound problems. The new plant would cause some additional sound, but Idaho Power would use a combination of noise-reduction measures like acoustic barriers, vibration isolation, silencers, and sound-absorbing materials to keep sound levels close to what you’d hear today at the industrial park.

Water

During typical operations, the Bennett Mountain Power Plant expansion would use about as much water as a couple average homes, primarily for potable purposes and washing equipment, cleaning, and periodically topping off storage tanks for the cooling system.

Idaho Power would not drill new wells for the expansion.

We recognize there are water constraints in the Mountain Home area and Elmore County. We aim to be a good neighbor that minimizes impacts by using water responsibly and managing it efficiently.

Community Partnership

For almost 110 years, Idaho Power has demonstrated a deep commitment to community partnerships. Construction would boost local businesses by bringing skilled trade professionals to the area. Idaho Power expects to hire several permanent employees to help operate both this expanded power plant and others in the area.

Schedule

• May 2025: The City of Mountain Home grants Idaho Power a conditional use permit for the proposed expansion at the Bennett Mountain site. 
• August 2025: Idaho Power files a Permit to Construct application with the Idaho Department of Environmental Quality. This permit would allow Idaho Power to begin plant operations.
• September 2025: Idaho Power receives a pre-Permit to Construct from the Idaho Department of Environmental Quality, allowing construction to begin.
• September 2025: Idaho Power submits a request for a Certificate of Public Convenience and Necessity (CPCN) to the Idaho Public Utilities Commission. If approved, the CPCN would recognize the value of the Bennett Mountain expansion to Idaho Power customers. It is a key step in the project’s permitting process.
• Spring 2026: Construction scheduled to begin on Bennett Mountain expansion.
• 2026: Idaho Public Utilities Commission’s decision on the CPCN is expected.
• Fall 2026: The Department of Environmental Quality’s decision on the Permit to Construct is expected.
• 2028: Anticipated completion of the Bennett Mountain expansion and start of plant operations.

Questions?

Contact Steve Smythe at ssmythe@idahopower.com.