Energy Generation

Resource Plan

Our Resource Plan identifies research and development projects and the most cost-effective combination of resources for meeting our customers’ needs for reliable electric service during the next 15 years. While this filing is required only in Minnesota (Docket Number 16-386), we develop a strategy for our whole system and file the plan with the North Dakota and South Dakota regulatory commissions.

Our 2017-2031 Resource Plan, approved by the Minnesota Public Utilities Commission (MPUC) in April 2017, gives us authority to add up to 250 Megawatts (MW) of natural gas, up to 300 MW of wind, and up to 30 MW of solar resources. To execute our resource plan, we're adding the Merricourt Wind Energy Center and Astoria Station to our resource mix. And, as solar prices continue to drop, we’ll likely build or purchase solar resources in the 2022 timeframe.

Resource Mix

The graphs below represent the energy we serve our retail customers.

 *The majority of our purchased power comes from Midcontinent Independent System Operator, Inc. (MISO). The makeup of our 2019 purchased power as shown on MISO's website is 41% coal, 31.2% natural gas, 16.9% nuclear, 7.8% wind, 1.8% hydro, and 1.2% other (includes solar). 

Renewable Portfolio Standards

Each of the states we serve has enacted either a Renewable Portfolio Standard or a voluntary Renewable Energy Objective. Minnesota requires 20% of the energy we serve our Minnesota retail customers to come from renewable resources by 2020 and 25% by 2025. The state also requires 1.5% of our energy for Minnesota retail customers to be generated by solar resources by 2020. We're well positioned to comply with Minnesota's renewable energy standard, with over 15% of our resources coming from renewables today. That percentage will increase when the Merricourt Wind Energy Center is energized in 2020. Additionally, we've purchased Solar Renewable Energy Credits to comply with the solar energy standard through 2021 and anticipate building or purchasing a large scale solar project by 2022. North Dakota and South Dakota implemented voluntary Renewable Energy Objectives for 10% of all electricity sold at retail to be obtained from renewable resources by 2015. We met those objectives.

Coal Power

We operate three coal-fired plants that produced about 46% of the energy our customers used in 2019.

Coal-fired Plants

Location: Big Stone City, SD

Age: On line since 1975

Capacity: 475 MW (Net Dependable Capacity)

2019 net energy output: 2,619,088 MWh

2019 availability: 91.43%

Fuel source: Subbituminous


  • 53.9% Otter Tail Power Company
  • 23.4% NorthWestern Energy
  • 22.7% Montana-Dakota Utilities Co.

Location: Beulah, ND

Age: On line since 1981

Capacity: 432 MW (Net Dependable Capacity)

2019 net energy output: 2,061,699 MWh

2019 availability: 67.67%

Fuel source: Lignite


  • 35% Otter Tail Power Company
  • 30% Northern Municipal Power Agency
  • 25% Montana-Dakota Utilities Co.
  • 10% NorthWestern Energy

Location: Fergus Falls, MN

Age: Unit 2 on line since 1959, Unit 3 on line since 1964

Capacity: 141 MW (Net Dependable Capacity)

2019 net energy output: 313,359 MWh

2019 availability: 84.4%

Fuel source: Subbituminous

Ownership: 100% Otter Tail Power Company

Hoot Lake Plant retirement

In 2012 we completed a baseload diversification study with a focus on evaluating retirement and repower options for our 1950s-era Hoot Lake Plant in Fergus Falls, Minnesota. The aging plant no longer is part of an economical resource plan, and we’ll retire the plant in May of 2021. We’re proud of Hoot Lake Plant’s legacy and the vital role it has played both in our company’s and community’s history. We're encouraging and assisting, when possible, the employees currently at Hoot Lake Plant to continue their career with our company. And we’ve been, and will continue to be, actively involved with the City of Fergus Falls to manage the impact of the planned retirement. The Merricourt Wind Energy Center and Astoria Station are part of our company’s plan to prepare for the retirement of Hoot Lake Plant, meet our customers’ future energy needs, and replace expiring power purchase agreements.

Wind Power

Wind farms in North Dakota, Minnesota, and South Dakota provide approximately 14% of our customers’ energy needs. With the resources already in service and the planned resources included in our Resource Plan, we will have wind energy in excess of our states’ standards and objectives.

Wind Farms

North Dakota Wind II (Edgeley): 21.0 MW Purchased

Langdon Wind Energy Center: 40.5 MW Owned, 19.5 MW Purchased

Ashtabula Wind Energy Center: 48.0 MW Owned

Luverne Wind Farm: 49.5 MW Owned

Ashtabula III Wind Energy Center: 62.4 MW Purchased

4.0 MW Purchased

.1 MW Purchased

Merricourt Wind Energy Center

Construction of the Merricourt Wind Energy Center began in August 2019. We expect the 15-month construction process to create more than 150 jobs and provide millions of dollars in economic benefits to the local area. The project will cost approximately $258 million, generate enough energy to power more than 65,000 homes, and add 10 permanent jobs to the local economy. The project includes 75 Vestas wind turbines and covers approximately 14,000 acres of land. The Merricourt Wind Energy Center will be the largest capital project in our history.

Natural Gas/Oil Power

Combustion turbines produce less than 1% of our company’s energy. 

Combustion Turbines

Capacity: 42.8 MW (Net Dependable Capacity)

2019 net energy output: 52,970 MWh

Fuel source: Natural gas or fuel oil

Capacity: 41.5 MW (Net Dependable Capacity)

2019 net energy output: 456.7 MWh 

Fuel source: Fuel oil

Capacity: 20.1 MW (Net Dependable Capacity)

2019 net energy output: 251.2 MWh 

Fuel source: Fuel oil

Astoria Station

Construction of Astoria Station, our 245 MW simple-cycle natural gas combustion turbine in Deuel County, South Dakota, began in May 2019. The station will have flexible operating options—providing energy during periods of high demand—with low emissions. We'll invest approximately $158 million in the project, which we expect to complete in 2021. We estimate that the project will create an average of 50 construction jobs, with a peak of 70 during the height of construction. That equates to approximately $30 million in construction labor costs. And, when complete, the station will require two to three full-time employees to operate it.

Hydro Power

We own six small hydroelectric plants in Minnesota that account for about 1% of our energy. The Bemidji hydro plant is on the Mississippi River, and the other hydro plants are on the Otter Tail River near Fergus Falls.

Hydro Relicensing Process

In 2016 we began the five-year process to relicense our five hydroelectric plants along the Otter Tail River. We've proposed to the Federal Energy Regulatory Commission (FERC) to relicense the plants as they are today because relicensing is more cost effective than alternatives for our customers—and because doing so will maintain reservoirs where customers and community members have built homes. The Fergus Falls community has grown and thrived alongside the plants for more than a century.