How the Co-Ops are Coping: Colorado Distribution Cooperatives and the ‘Green Energy’ Transition

By Ethan Cornell*

Introduction

Colorado’s electric distribution cooperatives are undergoing a period of rapid and uneven transition as they renegotiate wholesale power contracts, diversify their resource portfolios, and respond to state-level decarbonization pressures. The landscape is defined by three major suppliers: Tri-State Generation and Transmission, Guzman Energy, and CORE Electric Cooperative, which are pursuing strategies to maintain reliability while integrating renewables. As co-ops exit legacy contracts and add local solar and storage, the resulting mix of power supply arrangements has become increasingly complex.

This report seeks to compile and evaluate the current and planned power-supply arrangements for Colorado’s distribution cooperatives, to the extent possible, based on publicly available filings and reports in an attempt to identify emerging trends across the state. It then analyzes resource adequacy projections for the three most consequential players in the co-op space: Tri-State, Guzman, and CORE. Altogether, this assessment provides a clearer picture of the risks, gaps, and developing opportunities shaping Colorado’s cooperative electricity sector over the next decade.

The Biggest Players

CORE Electric Cooperative is Colorado’s largest electric distribution co-op, serving a broad area along the Front Range. It owns approximately 25 percent of Comanche Unit 3, but it is now exiting that ownership. In 2023, CORE struck a 20-year wholesale power agreement with Invenergy to deliver more than 1.2 terawatt-hours/year starting in 2026. This change is supported by CORE’s efforts to reduce carbon emissions by 80 percent by 2030 [xiii]

CORE’s Resource Additions (Starting 2026)

Core Resource Adequacy

CORE’s resource adequacy report contains several inconsistencies that raise concerns about the transparency and reliability of its long-term planning. While the accredited-capacity assumptions for renewables are appropriately conservative and broadly aligned with proper methodologies, the report simultaneously assumes 187 MW of dependable capacity from Comanche 3 through 2029, despite CORE’s public declaration that it is withdrawing from ownership of the plant. Counting the full accredited capacity of a unit they are actively attempting to exit creates a discrepancy between CORE’s stated strategy and the resource mix presented in the tables. Additionally, the report introduces large blocks of “New Capacity” in future years—324 MW in 2026—without disclosing whether these are contracted resources, pending PPAs, or simply placeholders used to meet modeled reserve margins. This lack of specification makes it difficult to evaluate whether CORE’s future portfolio is truly secured or merely anticipated. Collectively, these issues suggest that while the report meets formal compliance requirements, it does not provide a fully realistic depiction of CORE’s evolving power-supply position.

Tri-State Resource Adequacy

The projected energy demand Tri-State must meet remains relatively flat, hovering around 2,900 MW throughout the decade. The amount of power from Tri-State’s owned generation assets, primarily coal and gas, is scheduled to decline sharply, dropping nearly 53 percent from 1,793 MW in 2025 to 848 MW by 2030. This represents the retirement of substantial generation capacity. The total supply capacity remains above forecast load in the early years, starting at 3,267 MW in 2025. The surplus shrinks to just18 MW by 2029, then turns into a projected capacity deficit of 11 MW in 2030, widening to 567 MW by 2033.[xiv]

Guzman Resource Adequacy

Guzman Energy is shifting toward a high-renewable energy portfolio, adding over 200 MW of new wind, 80 MW of new solar, and 150 MW of battery storage over the next few years. Guzman is also adding a new gas asset (320 MW) by 2027/2028 to ensure generation availability when renewables are low. While Guzman’s investments are sufficient to meet the firm obligation load (62 MW), the projection shows they will fail to meet their own target planning reserve margin of 15 percent. The forecasted reserve margin drops from 8.3 percent in 2028 to 5.4 percent by 2030, creating a capacity deficiency of between 6.7 and 9.6 percentage points relative to the target. This shortfall shows a near-term compliance issue where Guzman will need to acquire firm, accredited capacity to close the gap. The underlying reason for this gap is the intermittent resources’ accredited capacity of solar (45 percent) and wind (15 percent), according to Guzman’s internal calculations.[xv]

Conclusion

Colorado’s cooperative utilities are charting divergent paths, but several patterns are clear. Tri-State faces a shrinking cushion between available capacity and load, driven by large coal retirements and an increasing dependence on purchased power. Guzman Energy, while aggressively expanding wind, solar, and storage, is projected to fall short of its own reserve margin targets unless it secures additional firm capacity. Meanwhile, CORE’s resource adequacy report raises credibility concerns, as it relies on capacity from assets it plans to exit and introduced substantial “new capacity” without clarifying contractual commitments.

Despite these challenges, Colorado’s distribution co-ops are steadily increasing renewable penetration. Whether these shifts can maintain reliability while meeting decarbonization goals will depend on clearer long-term planning, transparent reporting, and strategic procurement of accredited resources. As the state’s demand profile evolves and coal retirements continue, careful coordination among co-ops and their suppliers is essential to ensure resource adequacy and affordability.

[i] https://garnetmesasolar.com

[ii] https://tristate.coop/lpea-and-tri-state-execute-term-sheet#:~:text=LPEA%20will%20enter%20into%20two,lasting%20through%20December%2031%2C%202033

[iii] https://mercuria.com/la-plata-electric-association-agreement-with-mercuria-locks-in-affordable-reliable-energy/

[iv] https://tristate.coop/san-miguel-power-association-tri-state-announce-additional-support-and-investment-montrose-county#:~:text=Electric%20co,facility

[v] https://tristate.coop/tri-state-purchases-two-western-colorado-solar-projects-juwi#:~:text=,Empire%20Electric%20Association’s%20service%20territory

[vi] https://www.gvp.org/CoopPower#:~:text=Grand%20Valley%20Power%C2%A0has%20a%20long,hydroelectricity

[vii] https://mpei.com/power-transition#:~:text=MPE%20announces%20a%2020,PSA%29%20with%20Guzman%20Energy

[viii] https://www.guzmanenergy.com/united-power-tri-state-generations-largest-member-inks-deal-to-buy-electricity-elsewhere/#:~:text=United%20Power%20said%20Wednesday%20that,State

[ix] https://www.holycross.com/our-system/our-power-supply#:~:text=Holy%20Cross%20Energy%20,7MW%20of%20solar

[x] https://www.holycross.com/blog/new-clean-energy-projects-in-2024#:~:text=,Storage

[xi] https://www.businesswire.com/news/home/20230601005809/en/Yampa-Valley-Electric-Association-Announces-15-year-Wholesale-Power-Supply-Partnership-with-Guzman-Energy

[xii] https://tristate.coop/tri-state-purchases-two-western-colorado-solar-projects-juwi#:~:text=,end%20production%20later%20this%20decade

[xiii] https://wwww.invenergy.com/news/landmark-power-supply-partnership-between-core-electric-cooperative-invenergy-to-lead-colorado-s-energy-transformation

[xiv] https://tristate.coop/sites/default/files/PDF/resourceplan/Resource_Adequacy_2025.pdf

[xv] https://www.guzmanenergy.com/wp-content/uploads/2025/07/Resource-Adequacy-Report-2025.pdf

*Ethan Cornell is pursuing a master’s degree in natural resources and energy policy at Colorado School of Mines and is a recent graduate of the Future Leaders Program at Independence Institute.