Our customers count on safe, reliable power every day, even during heat waves and winter storms. That’s why we’re excited about the progress on Lange II, a new generating station under construction in Rapid City. Once complete, it will strengthen the reliable service our customers depend on.

We recently hosted local media at the Lange II site to share an update on construction. “We’re about at the halfway point of Lange II, which is a major milestone for this project,” said Wes Ashton, vice president of South Dakota and Wyoming Utilities. Crews are making steady progress, and the project is ahead of schedule, with plans to place the facility into service by the end of the year.

What is Lange II?

Lange II is a 99-megawatt natural gas–fired power plant being built next to the existing Lange I facility. When it comes online in the second half of 2026, it will help serve customers across western South Dakota, northeastern Wyoming and southeastern Montana. The plant will be especially important during times of high demand and extreme weather.

Why we’re building Lange II

Reliability is the driving force behind Lange II; customers expect dependable power every day, and this project helps meet that expectation. The timing is intentional, as several older generators at the Ben French plant, which have been in service since the 1960s, are scheduled for retirement in 2027. Lange II will replace those units with modern technology built to deliver safe, affordable and reliable energy for decades.

How Lange II will operate

The facility will use six large dual-fuel engines that primarily run on natural gas, with the ability to operate on diesel if needed. Each engine can power thousands of homes and can start up quickly, reaching full output in under five minutes. That fast response makes Lange II well suited to support the electric grid during sudden changes or outages.

The plant is designed with resilience in mind. Dual-fuel capability, on-site fuel storage and underground natural gas storage will allow it to continue operating even during supply interruptions. The engines are also efficient with water use, and the building is designed to reduce noise to minimize impact on nearby neighbors.

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Where construction stands today

Construction began earlier this year following site preparation, and work is now focused on the main building structure. All six engines have arrived in Rapid City after being shipped from Finland. Favorable winter conditions allowed work to move faster than expected.

“We didn’t have the moisture you would usually expect or the muddy spring conditions, so that’s allowed construction to proceed very well,” Ashton said. “We’re ahead of schedule.”

At peak activity, about 225 workers will be onsite, many from local companies. The project is providing near-term economic benefits and will generate long-term property tax revenue for Pennington County.

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The value for our customers

Lange II is an intentional, long-term investment to serve the region and provide increased reliability now and in the future. We want our customers to know they can count on having power during heat waves, winter storms and other high demand events.

Once operational, Lange II will work alongside the existing Lange I facility, which has been providing about 40 megawatts of power to Rapid City and the Black Hills region since the early 2000s. Together, the two plants will strengthen local generation.

“Lange II will allow us to continue to serve Rapid City and the Black Hills region for decades to come,” Ashton said. “We want to make sure we continue to provide safe, reliable, cost-effective energy to our customers.”