Idaho Power announced the completion Thursday of an $18 million substation upgrade at its Karcher facility in Nampa, a project that doubles the electrical capacity serving southern Canyon County and ensures reliable power delivery to the thousands of new homes, businesses, and industrial operations coming online in one of Idaho’s fastest-growing regions. The upgrade was completed three months ahead of schedule and below budget, a feat that Idaho Power CEO Lisa Grow attributed to favorable construction conditions and strong contractor performance.
The Karcher substation serves approximately 35,000 residential and commercial customers across southern Nampa, Caldwell, and unincorporated Canyon County. Peak electrical demand in the substation’s service area has grown approximately 6% annually over the past four years — roughly double the statewide average — driven by the rapid residential construction boom and the expansion of commercial and agricultural processing operations throughout Canyon County.
What the Upgrade Includes
The project installed two new 138-kilovolt transformers, upgraded switching equipment, expanded the substation footprint to accommodate future capacity additions, and installed modern digital monitoring systems that allow Idaho Power’s grid operations center in Boise to detect and respond to equipment issues in real time. The digital systems replace analog monitoring equipment installed in the 1980s that provided limited visibility into the substation’s operating conditions.
“This substation was approaching its rated capacity, which meant that during peak summer demand — hot afternoons when every air conditioner in Canyon County is running — we had very little margin for error,” said Idaho Power distribution engineering manager Steve Johnson. “The upgrade gives us the capacity headroom to serve Canyon County’s growth for the next 15-20 years without reliability concerns.”
Reliability Impact for Canyon County
The upgrade is expected to significantly reduce the frequency and duration of power outages in the Karcher service area. The substation experienced 14 unplanned outage events in 2025, affecting a combined total of over 80,000 customer-hours of lost service. The new equipment includes automated switching capability that can reroute power around equipment failures in seconds rather than the hours required for manual switching under the old configuration.
Reliable electricity is particularly critical for Canyon County’s agricultural processing operations, where power interruptions can damage temperature-sensitive products, halt production lines, and create food safety concerns. Amalgamated Sugar’s Nampa plant, the J.R. Simplot Company’s Caldwell operations, and dozens of dairy operations across Canyon County all depend on uninterrupted power service from the Karcher substation.
Funding and Rate Impact
The $18 million project was funded through Idaho Power’s capital improvement program, which is supported by existing rates and does not trigger an additional charge for Canyon County customers. However, the investment will be included in Idaho Power’s rate base — the total value of assets on which the utility earns a regulated return — and will be a factor in the company’s pending rate case before the Idaho Public Utilities Commission.
Idaho Power noted that infrastructure investments like the Karcher upgrade are essential to maintaining the reliability standards that customers expect, particularly as the utility’s service territory continues to experience some of the fastest growth in the western United States. The company is planning similar substation upgrades at two additional Canyon County locations — the Middleton and Caldwell South substations — over the next three years.
What Comes Next
Idaho Power’s next major Canyon County project is the Middleton substation expansion, scheduled for construction beginning in fall 2026. Customers experiencing power quality issues or outages can report them to Idaho Power at 208-388-2323 or through the Idaho Power mobile app. For information about Idaho Power’s infrastructure investment program and the pending rate case, visit idahopower.com.