Black Hills Energy completed construction on a 260-mile, $350 million transmission expansion project that will interconnect electric systems in Wyoming and South Dakota, while expanding the footprint of CAISO’s Western Energy Imbalance Market.
Black Hills Energy completed construction on a 260-mile, $350 million transmission expansion project that will interconnect electric systems in Wyoming and South Dakota, while expanding the footprint of CAISO’s Western Energy Imbalance Market.
The transmission line is part of Black Hills’ Ready Wyoming electric transmission expansion project and directly connects Black Hills subsidiaries Black Hills Power and Cheyenne Light, Fuel and Power.
The line was energized and placed in service in December, the company said in a Jan. 7 announcement.
“This transformative project will benefit our customers for decades to come, supporting our success in providing long-term value by delivering reliable and cost-effective energy to our customers,” Linn Evans, CEO of Black Hills Corp, said in a statement. “Ready Wyoming reduces reliance upon third-party transmission and allows us to provide customers with the value of expanded access to energy markets.”
In 2024, Black Hills Power and Cheyenne Light announced they would move from SPP’s Western Energy Imbalance Service to CAISO’s WEIM. (See CAISO’s WEIM Plucks Black Hills Utilities from SPP’s WEIS.)
The decision would expand the WEIM’s presence in Montana and Wyoming and extend its footprint eastward to take in a slice of South Dakota, which would become the 12th state included in the market.
Under the WEIM implementation agreement signed by Black Hills Power and Cheyenne Light, the utilities agreed to register a new balancing authority to facilitate participation in the market by 2026.
The newly energized 260-mile line is part of Cheyenne Light’s FERC tariff and will be within the WEIM when the utility begins participation in May, according to Black Hills.
“The project is expected to maintain long-term cost stability for customers, enhance system resiliency and access to power markets, support local economic growth and facilitate future development of energy resources in Wyoming,” Black Hills said in a news release.
Black Hills plans to recover approximately $300 million of the total transmission investment through the company’s transmission rider and recover about $50 million of the remaining distribution investment through base rates, according to the news release.
Black Hills could also play a role in the competition between CAISO’s Extended Day-Ahead Market and SPP’s Markets+. Black Hills and NorthWestern Energy announced a merger in August 2025, and the two entities’ sprawling territories could shape the footprints of the two competing Western day-ahead markets in key ways, although NorthWestern — a WEIM member — has not publicly signaled a leaning toward either day-ahead market. (See Black Hills-NorthWestern Merger Could Reshape Western Market Map.)
The deal requires federal and state approvals.
Black Hills Energy’s Colorado subsidiary has recently filed with that state’s utility commission for approval to join Markets+. (See Black Hills Colorado Seeks Approval to Join Markets+.)
