Coolidge Expansion Project FAQ

As a community-based, not-for-profit utility, SRP makes decisions in the best interest of our customers and the communities we serve.

When deciding how to meet the rapidly growing electricity needs in one of the country's fastest-growing regions, SRP examined which generating resources could meet its increasing resource needs. As a result of that review, SRP determined that expanding the existing Coolidge plant was the best option to meet near-term capacity needs.

This doesn't change SRP's commitment or plans to reduce carbon; in fact, the Coolidge Expansion Project (CEP) helps by ensuring reliable energy while we work to integrate more solar, battery and other renewable resources into the grid.This project and other strategic resource additions will help us meet our goal of cutting carbon emissions by 82% from 2005 levels by 2035. Our diversified energy portfolio taps into the most efficient, available and cost-effective mix of generation resources.

SRP continues to see higher-than-average increasing customer demand across our service area, one of the fastest-growing regions in the country. Our service territory continues to see a population increase more than double the national average. In addition, SRP is experiencing major industrial and manufacturing growth from large companies establishing and expanding operations in the region.

This growth causes SRP's peak electricity demand to increase significantly. Specifically, we are forecasting growth in peak electricity demand of approximately 2,300 megawatts (MW) by 2030, which represents an increase of nearly 30% from today.

A combination of this growth and the region's overall resource constraints means that without proper planning, Arizona utilities will be challenged to meet customers' needs in the very near future.

In 2022, third-party energy consulting group E3 concluded that the Southwest is facing "a significant and urgent need" for new power resources due to growing demand and planned fossil fuel plant retirements.

California officials reported a 1,700 MW potential shortfall in 2022, which could go even higher if environmental factors like fires continue to impact generation. The reports indicated that those kinds of supply gaps could leave between 1 million and 4 million people without power. And the New Mexico Public Service Co. recently told regulators it does not have any capacity reserve margin for July or August.

Supply chain and other issues are also contributing to constraints. A U.S. Commerce Department investigation has negatively impacted solar panel supply chains, and all of the solar projects that SRP has under contract to begin operation in 2024 are at risk of delays and cost increases. Lithium costs are skyrocketing, and the supply chain for batteries is also experiencing challenges, resulting in potential delays and higher costs.

The expansion of the Coolidge Generating Station would add 575MW of capacity that can vary during the year because of changes in temperature and humidity. The power would be produced by 12 natural gas turbines, each capable of ramping up to full production within 10 minutes. The flexible nature of these turbines allows one or more of the turbines to power up to meet demand in different system conditions.

Along with increased solar generation comes increased variability in power output, especially during cloudy conditions. The CEP will add quick-starting and fast-ramping power generation resources that can smooth out these fluctuations and ensure SRP delivers consistent, reliable power to customers.

Each gas turbine added as part of the CEP will be capable of rapid starts (within 10 minutes) and can quickly adjust to match changing electricity demand across the Valley. In addition, the flexibility of this technology allows SRP to operate just one or two turbines when needed, versus having to run all of them at the same time.

SRP anticipates and is planning to add more battery storage projects in the coming months and years as the technology matures. We are an early adopter of battery technology and as of 2025 have 1,100 MW of batteries online — among the highest of any utility in the West.

Adding battery storage over the next three years in the amounts required to achieve similar reliability as the proposed Coolidge expansion gives us pause. Increasing battery storage at a measured pace, however, allows us to gain operational experience as the technology evolves. This approach will also help us benefit from decreases in battery prices and increases in storage duration that we expect to occur.

We don't have much operational experience with batteries, particularly long-term operating experience. That's also true for the utility industry as a whole. As of the end of March 2023, there was only approximately 9,500 MW of battery storage online in the United States — that's less than 1% of total U.S. generation capacity.

This technology is also still developing and we are committed to incorporating it safely and appropriately to help meet the energy needs of our customers and community.

When we consider investing in a new power generation resource, we carefully consider alternatives in the context of reliability, our 2035 Sustainability Goals and affordability for our customers.

In evaluating options for the Coolidge Expansion Project (CEP), we:

1. Used commercially available planning models to determine whether we could build a portfolio of zero-carbon resources that could achieve the same reliability as the Coolidge plant expansion, and
2. Retained E3, an economic and environmental consulting firm, to provide an independent perspective on the same issue. E3 used its own proprietary planning model to build a zero-carbon portfolio that achieves similar reliability as the CEP.
3. In addition, we evaluated different sensitivities, including higher natural gas prices and lower battery costs than our current forecasts suggest.

As a result of the variability of renewables like solar and wind and the limited duration of battery storage, both our assessment and E3's assessment independently concluded that SRP would need to build three to four times the megawatt capacity of zero-carbon resources (primarily solar and batteries) to achieve similar reliability as the Coolidge expansion.

The Coolidge portfolio was the lower-cost option in all scenarios and did not impact our ability to meet or exceed Board-established carbon reduction commitments. The Coolidge portfolio resulted in $342 million to $872 million of savings (in today's dollars) compared to the zero-carbon portfolio. This analysis demonstrates that Coolidge is not just the most prudent and practical decision but also is the best economic decision that provides the most value to SRP's customers.

The 12 new generating units that would be added at the Coolidge Generating Station will look nearly identical to the 12 existing units that currently operate at the plant. The stacks for the existing 12 units are approximately 85 feet tall and we expect the stacks for the new units will be a similar height.

SRP recognizes that the existing power plant is located adjacent to Randolph, a historically African American community in an unincorporated area of Pinal County.

This project would expand the existing plant by adding new turbines that comply with all state and federal regulations. The facility was built between 2009 and 2011 with no opposition to its construction. From the start of its operation, SRP contracted the facility's output from the plant owner under a power purchase agreement. In 2019, SRP made the decision to purchase the facility, and to our knowledge and understanding, the facility has operated safely and with no safety complaints during its 10 years of operation to date.

As part of the expansion project, SRP will help mitigate the impacts of the expansion and support the Randolph community, including road paving, scholarships and job training, historical markers to formally recognize the community, and additional measures. This is a long-term commitment to help preserve Randolph's history and ensure its approximately 150 residents thrive in their homes for decades to come.

In cooperation with the community of Randolph, Pinal County and the City of Coolidge, SRP coordinated the formation of the Community Working Group (CWG), which meets bi-monthly.

The CWG is composed of five residents of Randolph, one member designated by the Pinal County Board of Supervisors, one member designated by the City of Coolidge, and two members selected by SRP. SRP will act as an adviser to the CWG and collaborate on projects to support the Randolph community.

We do not need to purchase any additional land for the proposed CEP. The expansion will be constructed on SRP-owned property directly to the south of the existing Coolidge Generating Station. 

Expansion at the existing Coolidge Generating Station allows us to leverage existing infrastructure, including access to transmission and fuel, reducing the overall cost of the project.

The CEP represents a substantial investment in the Coolidge region by SRP and will generate property taxes that are estimated to be nearly $52 million from 2025 through 2036. These property taxes would be spread across county ($13.5 million to Pinal County), city ($6.9 million to the City of Coolidge), schools ($22.2 million to Coolidge Unified Schools) and higher education ($7.8 million to Central Arizona College).

To meet SRP’s Board approved sustainability goals to reduce carbon intensity by 82% by 2035 and net zero by 2050 we are adding thousands of megawatts of solar resources to our system. Our diversified energy portfolio taps into the most efficient, available and cost-effective mix of generation resources. Learn more about our ongoing sustainability efforts as well as our plan for the future.

SRP has more photovoltaic (PV) solar contracted than any other Arizona utility. There is more than 900 MW of large-scale solar currently under development, which will bring SRP’s total solar energy to more than 2000 MW, once operational. In total, this will be enough to power more than 450,000 average-sized homes when the sun is shining, and solar plants are generating the most energy. There are also more than 900 MW of battery energy storage systems currently under development, which will bring SRP’s total battery storage capacity to more than 1,300 MW by the end of 2025. This is enough storage to power as many as 247,000 homes for up to four hours.

The CEP will enable the addition of more renewable resources while maintaining the reliability of SRP's power system. This makes the CEP an important contributor to meeting our goal of cutting carbon emissions by 82% from 2005 levels by 2035 and achieving net zero carbon by 2050.

The CEP will comply with all local, state and federal air quality regulations, which are protective of human health and the environment.

One such area of regulation is the Clean Air Act (CAA), which requires the United States Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six common air pollutants — called "criteria" pollutants.

This is designed to protect the public — including sensitive populations such as children and the elderly — from adverse health effects and to provide public welfare protection, including protection against decreased visibility and damage to animals, crops, vegetation and buildings.

To expand the Coolidge plant, SRP filed and received air permit, which ensures the emissions meet air quality regulations.

As part of the process to obtain a permit for the Coolidge expansion, SRP retained a consultant to conduct ambient air quality modeling to assess the impact of air emissions from the addition of the new units at Coolidge. Based on this review, it was determined that the new units will not cause or contribute significantly to a violation of any NAAQS.

The final air quality permit is a federally enforceable document containing applicable emission limits and standards that Coolidge is responsible for meeting and contains recordkeeping, monitoring and reporting conditions necessary to demonstrate compliance with all applicable requirements. For the most up to date information on the air permit click here.

The CEP generation method is simple cycle, which uses aeroderivative turbines similar to those used in the aviation industry. It does not rely on steam to produce power, so it uses significantly less water than other types of generation, such as a combined-cycle natural gas power plant.

Before the Coolidge site property was a natural gas generating site, the allowable groundwater use on the property was 736 acre-feet per year. After the proposed expansion, total water usage at Coolidge Generating Station is not expected to exceed 450 acre-feet per year — a 40% reduction in the water use previously allowed on the property.

After completion of the expansion, SRP will discontinue the use of groundwater and will rely exclusively on stored Central Arizona Project (CAP) water to serve the Coolidge Generating Station. SRP has already stored sufficient water in the Pinal County Active Management Area (AMA) to support an expanded Coolidge Generating Station for more than 60 years.

Construction activities began in the spring of 2024. We expect the completion and commercial operation of the first six natural gas turbines by Summer 2026 and completion of the second six no later than Summer 2027. This schedule includes work on the new 500 kV switchyard, modifications to the existing 230 kV switchyard and transmission lines. All construction will be taking place on SRP-owned land.

SRP has conducted multiple recent RFP processes, which have confirmed that the Coolidge Expansion Project provides the lowest-cost option for SRP customers. As part of those processes, we conducted a thorough and extensive review to evaluate options for the additional power generation needed.

The only resource options that could meet our significant capacity and flexibility needs in the time frame required are natural gas peaking units and battery storage. As explained in the responses above, we have concerns about the feasibility of adding the amount of battery storage that would be needed to achieve similar reliability to Coolidge in the time frame needed, and we demonstrated that the Coolidge Expansion Project is the lowest-cost option for our customers.

We selected the General Electric LM6000 turbine technology for the Coolidge Expansion Project based on three factors: reliability, flexibility and operational experience.

The LM6000 turbines are flexible resources that allow SRP to integrate more renewables into the power system. They can start up and change output quickly to support the variability of renewable resources. In addition, the flexibility of this technology allows us to operate just one or two turbines when needed, versus having to run all of them at the same time.

We must reliably meet near-term capacity needs, and the LM6000 turbines are available to provide power when needed, including during outages of other units or when limited-duration resources are unavailable. The LM6000 model is an industry leader in reliability with over 40 million operating hours and over 99% reliability.

In addition, the existing Coolidge Generating Station utilizes the LM6000 technology, providing operational familiarity and common spare parts to reduce maintenance costs.

The outreach process included a variety of mechanisms to inform the public about the status of the siting process and to solicit public input.

The process began when SRP announced the proposed project in a press release in August 2021 and then presented the project for approval at a Board meeting in September 2021. These meetings are open to the public.

From there, we conducted a public outreach process that included both virtual open houses and in-person open houses with appropriate COVID precautions in place. Both the in-person and virtual open houses gave the public an opportunity to provide comments on the project. The in-person open house allowed the public to review informational displays, submit comments to the SRP project team and provide valuable feedback.

We met with public officials representing the region, jurisdictional agencies and other stakeholders. In addition, postcards were mailed to announce the project and this website was developed to allow members of the public to obtain updates and additional information. We also used social media to inform the public about the open houses and opportunities to provide comments.

Notification will be mailed to nearby residents and communities before construction begins on the expansion project.

We have also established a dedicated hotline as another option for members of the public to ask questions and provide comments on the project: (602) 236-2872.

On June 21, 2023, the Arizona Corporation Commission (ACC) approved an amended Certificate of Environmental Compatibility (CEC) for the Coolidge Expansion Project, a flexible, fast-ramping natural gas plant that will help SRP cost-effectively and reliably meet the region’s growing energy needs as the utility works to add more solar, wind and storage resources.

SRP received an air permit authorizing the construction and operation of the CEP from the Pinal County Air Quality Control District. The most up to date information on the air permit can be found here.