Duluth, MN

Duluth Energy Systems

Transformation through Master Planning

Operations, maintenance, and management including business planning, project management, and engineering
City of Duluth, municipal utility
Plant Capacity
The system delivers 150 psi steam via a network of more than 10 miles of steam piping. The system is served by four 100,000 pound per hour steam boilers with a typical winter peak steam load of approximately 200,000 pounds per hour.
Number of buildings served
165 buildings in downtown and Canal Park
Distribution network length
10 miles
A system advisory committee includes local citizen, business, academic, non-profit and advocacy, and government stakeholders.

Duluth Energy Systems is the city-owned steam district energy system that has provided the Canal Park and Central Business Districts with stable, reliable heat since 1932. The system provides heating to 164 buildings and cooling to five buildings in Canal Park and downtown Duluth. This legacy system is still primarily steam-based, with a smaller hot water loop serving the Canal Park district. The plant is currently fuel flexible with the ability to use coal or natural gas, with potential for biomass commingling with the solid fuel boiler. In 2012, Ever-Green worked with the City of Duluth create a framework for the future of this system, starting with the steam-to-hot-water transition of the distribution system, beginning with 16 blocks of Superior Street in 2017. This phase was completed in 2018.

The City of Duluth has made its energy future a priority and has seized opportunities to work within the community, with its utilities, and in collaboration with experts from around the country to integrate state-of-the-art technology and international best practices for an efficient, cost-effective, and environmentally advanced system.

Ever-Green Energy’s Role: Ever-Green serves as the system operator and manager. Ever-Green is supporting the City in their effort to gain community support and state funding for system upgrades. This project has engaged experts and supporters from within and beyond Duluth, including state commissioners, city councilors, and executives from the business, energy, environmental communities who believe in Duluth’s grand energy vision.

Ever-Green works closely with the City of Duluth while we operate and manage this community energy system. Our team has guided the system through enhancements to the system’s operational and maintenance processes, including inventory management, operating and maintenance crew structure, work planning, performance monitoring, and trending of key parameters. Ever-Green reviewed the debt financing of the system and recommended changes, which enabled the system to enter into long-term contracts with customers and use revenue bonds for future debt financings. Recent areas of technical focus have included customer development, efficiency improvements, carbon reduction (through reduction of coal, plant and distribution improvements), steam to hot water transition, and future renewable integration.


  • Critical upgrades to Duluth Energy Systems − switching from steam to more efficient hot water and creating additional opportunities for proven technologies such as waste heat recovery and combined heat and power.
  • Helping Duluth building owners meet high standards for energy efficiency.
  • Integration of renewable energy that supports the local forest industry.
  • Utilize the system upgrade as an opportunity to grow the system and provide benefits back to current users, as well as extending the services to new users, promoting overall economic development opportunities.


  • 1932 system start-up.
  • 1979 change of ownership, the City of Duluth purchased the system.
  • 2012 Ever-Green was selected to serve as the operations and management team.
  • 2013 Ever-Green completed a comprehensive plan to modernize the energy system in a cost-effective manner that meets the current and future needs of users.
  • 2015 Duluth Steam transitioned to the new name Duluth Energy Systems and unveiled a set of goals to modernize the system and advance a grand energy vision for Duluth.
  • 2016 a bonding request was made to the State of Minnesota for matching funds to support the system transformation to coincide with the large public works project to rebuild Superior Street. Ever-Green begins design and engineering for the project.
  • 2017 The City of Duluth was awarded $15 million in state bonding to help modernize Duluth Energy Systems.
  • 2018 Phase 1 of the Superior Street Project was commissioned, renewable fuel oil agreement was signed, and the permit application was submitted

Technologies Implemented: Steam and hot water district heating, district cooling, absorption cooling, biomass, waste heat recovery.

Modernizing Duluth Energy Systems – Superior Street Project


Buildings served with district Steam: 164 Buildings
FY 2015 energy sales: 111,870 MWh
Total Building Area Served: 5.6 million square feet


Two coal boilers: 25 MW ea
Two Coal / Gas boilers: 28 MW ea
Total: 106 MW
Pipe Diameter: 1-inch to 20-inch
Pipe Length: 59,000 feet
Supply Pressure: 150 psi
Reliability rate: 99.992%


Buildings served with district hot water: 6 Buildings
FY 2015 energy sales: 17,360 MWh
Current billed demand: 2.65 megawatts
Total Building Area Served: 0.5 million square feet


Exhaust steam from auxiliary turbines (augmented by main steam as required)

Pipe Diameter: 4-inch to 12-inch
Pipe Length: 6,900 feet each, supply and return
Volume: 100,000 gallons
Supply Temperature: 190-220 degrees F
Return Temperature: 160-190 degrees F
Supply Pressure: 40 psi
Reliability rate: 99.992%


Buildings served with district cooling: 5
FY 2015 Energy Sales: 366,382 ton-hours
Building Area Served: 0.53 million sq. ft.


Chiller Plant 401 W First Ave

One Steam Absorption Chiller: 800 tons
Pipe Diameter: 4-inch to 12-inch
Pipe Length: 4,800 feet each, supply and return

Volume of distribution system: 15,600 gallons
Supply Temperature: 42 degrees F
Return Temperature: 56 degrees F
Supply Pressure: 30 psi
Minimum pressure differential: 15 psi
Reliability rate: 99.990%

Work with Ever-Green

Call 651.290.2812 or email info@ever-greenenergy.com to chat with an Energy Systems Expert.