The vision of APS is to create a sustainable energy future for Arizona. A sustainable energy future requires balancing the generation and delivery of reliable and affordable energy in unison with environmental stewardship, which for us translates to clean energy. To further our commitment to providing clean energy, we are adding nearly 1 gigawatt of clean energy projects by the summer of 2025. These projects include 850 megawatts (MW) of new solar storage with batteries and at least 100 MW of new solar generation.

By the end of 2018, more than 50% of our diverse energy mix was carbon free. We achieved this mix with a combination of traditional and renewable energy resources and energy efficiency actions, and we continue to make our energy mix cleaner by closing more coal units, modernizing natural gas plants, deploying renewable energy, installing battery storage and improving energy efficiency.

Read a recent feature by Chairman, President and CEO Don Brandt about collaborating on clean energy from EEI’s Electric Perspectives Magazine

APS Low-Carbon Economy Principles

APS’s transition to clean energy will contribute to a future low-carbon economy that will create new growth opportunities while providing environmental benefits. APS developed a set of principles to guide our path toward a low-carbon economy.

Read the APS Low-Carbon Principles.

Palo Verde Generating Station

For the 27th consecutive year, Palo Verde was the nation’s largest energy producer, generating 31.1 million megawatt-hours (MWh) of carbon-free electricity in 2018. Palo Verde is the only generating facility in the United States to produce more than 30 million MWh in a year, a milestone the plant has achieved 10 consecutive years and a total of 14 times. APS operates the Palo Verde Generating Station and owns or leases 29.1% of the facility.

Palo Verde has produced more carbon-free electricity than all the solar power plants built in California, and it does so reliably at all hours. Palo Verde supplies almost 70% of Arizona’s clean energy, and it even uses recycled wastewater for meeting its cooling needs.

Nuclear energy works in concert with renewable generation. Without nuclear energy, carbon emissions would increase because of greater reliance on natural gas to fill the inevitable energy void. Because Palo Verde is producing energy at all hours – day and night – it supports the basic needs of customers when solar and wind are not available because of their intermittent nature. It can facilitate increased adoption of electric vehicles (EVs) and improve the environment by supplying zero-emission energy to charge EVs and large-scale batteries instead of relying on natural gas- or coal-fired power plants to do the job.

Nearly half of Palo Verde’s output is dedicated to serving Arizona consumers. Electricity generated by the plant annually displaces more than 22 million metric tons of greenhouse gas (GHG) emissions that otherwise would have been produced, providing clean energy that powers about four million homes and businesses throughout the Southwest.

Read more about Palo Verde delivering clean energy 24/7.

Solar Resources and Research

We are a national leader in solar energy, with more than 1.4 gigawatts of solar capacity producing energy for our customers in Arizona. Our customers can count on us for innovative solutions that will advance Arizona’s solar leadership, including ground-breaking research to evaluate how energy companies can bring the benefits of this clean, renewable resource and advanced technology to customers reliably, fairly and affordably. Solar is an important part of our increasingly clean, diverse energy mix that will continue to grow in the future. We are setting the course for a sustainable energy future that brings together clean energy resources including solar, advanced technology, customer choice and reliability for all customers.

  • State Ranking. Arizona ranks No. 3 nationally for solar capacity
  • Solar Capacity. Our 1.4 gigawatts of solar capacity ranks No. 5 among all U.S. investor-owned energy companies
  • Solar Portfolio. Our portfolio includes 10 APS-owned large-scale plants, APS-owned rooftop solar systems and agreements to buy solar power from third-party providers, totaling 5.3 million solar panels (as of January 2019). We have helped more than 90,000 customers install private rooftop solar on their homes, and we have assisted more than 300 schools and more than 150 government agencies install solar projects at their facilities across Arizona.

Learn more about our Renewable Energy Portfolio.

APS is pursuing numerous opportunities to advance Arizona’s solar leadership for the benefit of customers here and across the nation.

APS engineers are developing and deploying innovative projects to understand solar’s potential for customers, including evaluating how solar interacts with energy storage and other advanced technologies.

Research from the award-winning APS Solar Partner program, Solar Innovation Study and APS Solar Communities program, among others, is being shared across the utility industry and with academic researchers, consumer advocacy groups and Arizona-based solar installers.  The results are informing our company and the industry about how to bring the benefits of solar energy and advanced technology to customers reliably and affordably.

Learn more about our Solar Research projects.

Energy Storage

APS recently announced that we will add 850 MW of battery systems and at least 100 MW of new solar generation by 2025, for a total of 950 MW of new clean energy technology. This represents a major down payment on Arizona’s continued progress toward an energy future that is clean, reliable and affordable.

Adding Storage to Existing Solar Plants. APS owns and operates large-scale solar plants throughout the state that will be upgraded with 200 MW of battery storage systems. Six new battery systems will be in place at our solar plants by 2020, with the remaining two upgrades to be completed by 2021.

Building New Solar Storage Plants. APS plans to build an additional 500 MW of solar storage and stand-alone battery systems by 2025. We issued a request for proposal for the first project, a 100-MW solar-plus-storage plant. APS is also partnering with Tempe-based First Solar on a solar-plus-storage project that will include a 50-MW battery fueled by a 65-MW solar field. The facility will be completed in 2021.

Delivering More Clean Energy When Needed. When solar production declines late in the afternoon and energy usage is still high, energy companies need a reliable, flexible source of power to serve their customers. Traditionally, that source has been exclusively natural gas. Today’s announcement signals a new direction: APS will use 150 megawatts of solar-fueled battery storage to meet part of the demand when energy usage peaks. The battery storage will come from two projects: a 100-megawatt battery provided by AES, and a 50-megawatt battery by Invenergy. Additional natural gas will come from a contract with Calpine for 463 megawatts of energy; however, instead of a traditional 20-year contract, the purchase agreement with Calpine is seven years, allowing APS the flexibility to take advantage of cleaner technologies in the future as they mature. This is part of a long-term clean-energy transition in which renewable and storage technologies will play an increasingly important role.

Learn more about all our energy storage projects.

Coal Reduction

We have a long history of transitioning to clean energy resources that reduce carbon emissions. One important factor in this transition is the closure of coal-fired generating units. Our coal reduction plan is expected to decrease the share of coal-fired energy in our generation mix from its current level of 21% to about 15% by 2020.

We have permanently retired four coal-fired units since 2013 – one unit at our Cholla Power Plant (2015) and three units at our Four Corners Power Plant (2013) for a total of 820 MW, which resulted in a reduction of carbon emissions of approximately 28%. Plans call for the end of all coal-burning generation by Navajo Generating Station (315 MW) in 2019, increasing our total to 1,135 MW retired by the end of 2019. In addition, we have committed to end the use of coal at our remaining Cholla units by 2025.

Climate Concerns

APS recognizes that energy companies face a unique challenge when it comes to reducing GHG emissions. For more than a century, the majority of electrical energy has been generated with carbon-based fuels. Transitioning to a decarbonized generation resource mix is a long and expensive undertaking. However, APS has been moving toward a lower carbon position for many years.

We also have proactively increased our system resiliency, implemented forest management programs to mitigate the risk of wildfires, and developed rapid-response plans to promptly restore power after storms.

A changing climate may present more challenges with providing reliable and affordable energy to customers. Therefore, APS participates in various research and policy organizations, such as the Electric Power Research Institute, Edison Electric Institute, Center for Climate and Energy Solutions and the Center for a New Energy Economy. This participation helps us understand varied perspectives on climate change and the value of effective and actionable carbon-reduction strategies.

Carbon & Air Emissions

At the onset of the Paris Agreement, the United States set a target of a 28% reduction from 2005 GHG emission levels by 2025. APS met this GHG reduction goal nine years ahead of schedule. Since 2005, APS’s annual GHG emissions have been reduced by almost 5 million metric tons, which represents a 28% reduction.

As Arizona’s population grows, APS plans to provide the increased energy required to support this growth as efficiently as possible relative to carbon emissions. We set long-term carbon emission goals based on our carbon intensity, as measured by the pounds of carbon emission per MWh of energy. By 2032, we expect our carbon-emission rate to decrease to less than 600 lb/MWh, which is a 48% reduction from our 2005 baseline year.

In 2018, the total APS carbon dioxide emissions were 13,137,903 tons. This represents an increase of 11.1% over total carbon dioxide emissions in 2017. The 2018 increase is attributable to greater utilization of coal-fired generation, especially the Four Corners units. The increased utilization of the coal-fired units was due primarily to two reasons. First, in 2018 the Four Corners units returned to service after major unit outages in which the units were retrofitted with selective catalytic reduction (SCR) technology—a technology that dramatically reduces nitrogen oxide emissions. As a result, the operation of these units increased in 2018. The other contributing factor was an increase in natural gas prices. The average natural gas price in 2018 was 16% higher than the previous three-year average. 

However, when viewed with a longer-perspective lens, the trend is still towards reduced carbon emissions. Compared to just three years ago, the total company carbon dioxide emissions have decreased by 12.2%, and the percentage of total carbon dioxide emissions from coal-fired units has decreased almost 10%. While we expect year-over-year carbon emissions to vacillate, the long-term trend for carbon dioxide emissions continues to be on a downward trajectory.

In addition to carbon reductions, we on the pathway to reduce nitrogen oxide (NOx) and sulfur dioxide (SO2) intensity by 93% and 89%, respectively. Since 2005, we have had an intensity reduction of 77% for NOx and 86% for SO2. This resulted from our commitments to reduce emissions and institute operational efficiency enhancements.

Carbon Management

APS reduces its environmental impact by closing older, less-efficient coal units and upgrading environmental controls on newer units. SCR technology currently is employed at six of our power plants. As noted above, installation of two new SCRs at the Four Corners Power Plant in 2018 resulted in an 88% NOx reduction at that facility.

Learn more about our air emissions trends.


We believe it is important to disclose our carbon management strategies and GHG emissions to customers, investors and other stakeholders. APS voluntarily reports annually to the CDP (formerly the Carbon Disclosure Project), a global nonprofit organization that collects and analyzes environmental data for investors to use in financial decisions. This organization’s network of investors represents more than $100 trillion in assets. CDP reporting provides a benchmark to evaluate how well we manage our carbon emissions, climate change risk, and to identify opportunities for improvement.

We have participated in CDP since 2006. In 2018, our CDP reporting for climate change received a “Management” score (letter grade “B”), which puts APS in the top quartile for U.S. utilities for the action and approaches in managing climate change. This score is also higher than the electric utility average of C, and higher that the North American regional average of C. Our Scope 1, 2 and some of scope 3 GHG emissions reported to CDP are third-party verified.

In addition, we submit a comprehensive annual report of our GHG emissions to the Environmental Protection Agency (EPA) as required by federal law.

Learn more about our CDP responses and documents.

Carbon Management

To measure our overall carbon reductionnot just decreasing emissions from generation but also throughout our company operationswe use a carbon-avoidance metric. This reflects actions taken company-wide, including retiring coal units, installing renewable generation and energy efficiency, increasing our building and operating efficiencies, and pursuing fleet electrification.

In 2018, we avoided 4.5 million metric tons of carbon. Since 2015, APS has avoided 18.1 million metric tons of carbon dioxide emissions that otherwise would have been emitted had we not taken actions to reduce the emissions. That is equivalent to removing almost 4 million automobiles from the road.

Sustainable Fleet

The APS transportation fleet continues its conversion to more fuel-efficient vehicles and electrification by continually researching the market and updating the electrification strategy for our fleet. Through this ongoing conversion and by using our fleet more efficiently, we are working to reduce both carbon emissions and operating costs. The transition to hybrid technology in our fleet is driven by a favorable return on investment. Not only do we gain the benefits of hybrid technology, but our investment in hybrid vehicles does not exceed the cost of purchasing comparable petroleum-burning vehicles. We currently have a fleet of 27 sedans, of which 48% are plug-in hybrid electric vehicles. In addition, we are in the process of replacing all forklifts weighing 10,000 pounds or less with electric units.

New idle-mitigation technology is now standard on all trouble man trucks, allowing workers to run laptops and air conditioning without keeping the vehicle running. In addition to reducing our carbon footprint, this decreases noise when working in residential neighborhoods. Our Odyne bucket trucks use less fuel and have quieter operations than traditional diesel or gasoline engine trucks by using battery-assisted drivetrain and electric power takeoff (ePTO) technology while operating the bucket. We are currently evaluating the new idle-mitigation technology for adoption in our larger trucks.

Sustainable Facilities

Our commitment to reduce our environmental footprint through sustainable practices is evident throughout APS facilities. Our corporate headquarters in Phoenix has earned five ENERGY STAR labels for energy efficiency from the EPA. Over the past 11 years, we have improved energy efficiency at this facility by approximately 30%. Overall, APS facilities have received 10 ENERGY STAR labels. In 2018, our energy use decreased 6% compared to 2017 through efficiencies we implemented, resulting in a reduction of 1,156 metric tons of carbon dioxide emissions.

Sustainability strategies are embedded within our standard architectural and engineering specifications when managing changes to our buildings or constructing new space. We work to improve energy efficiency throughout our facilities by replacing obsolete building systems and equipment with more energy-efficient systems and equipment.

Our focus on green building principles was highlighted as part of a major construction project completed in 2018. Our final phase of renovation work completed within our DVN2 facility in Phoenix incorporated a wide range of sustainable design principles, materials and systems. Green features of the facility include use of LED lighting and electronic lighting controls, harvesting natural light through exterior windows and more than 100 roof skylights, higher efficiency mechanical systems, low-flow and low-flush water fixtures, thermal pane glass and low-VOC paint and flooring materials.

Going forward, proactive assessments of the health and use of our buildings, use of the most current technologies as we renovate, reusing materials where possible and further replacing ozone-depleting technologies will guide our decision-making. We will continue to design, construct, operate and maintain our new and remodeled facilities to ENERGY STAR standards and LEED principles.

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