We have undertaken a number of initiatives to address emissions related to climate change, including renewable energy procurement and development, as well as promotion of customer programs and rates that encourage energy conservation, renewable energy use and energy efficiency. APS currently has a diverse portfolio of renewable resources, including solar, wind, geothermal, biogas and biomass, and we expect the percentage of renewable energy in our resource portfolio to increase over the coming years. APS prepares an inventory of greenhouse gas (GHG) emissions from its operations. This inventory is reported to EPA under the EPA GHG Reporting Program and is voluntarily communicated to the public on Pinnacle West’s website. We have also participated in the CDP (formerly the Carbon Disclosure Project) Climate Survey since 2006. In 2016, CDP noted that we are “taking coordinated action” on climate change issues and graded our company above industry and regional averages for climate change management. In 2017, we had our Scope 1, 2 and 3 greenhouse gas emissions third-party verified. In addition to these efforts, other steps we are taking to reduce our greenhouse gas impact include sulfur hexafluoride (SF6) reduction activities and ash reuse.

SF6 Reduction Activities

APS has been accurately measuring and reducing SF6 emissions system-wide since voluntarily joining EPA’s SF6 Emission Reduction Partnership for Electric Power Systems in 2004. SF6 is an extremely potent greenhouse gas, having a global warming potential that is 22,800 times more effective at capturing the sun’s energy than an equivalent amount of carbon dioxide. APS primarily uses SF6 for insulation and current interruption in electric transmission and distribution equipment.

As part of our commitment to the ISO 14001 program, our goal is to continually improve our procedures and processes through self-assessments and investigations. In 2016, APS improved its monitoring and tracking of SF6 emissions by:

  • Standardizing and increasing the efficiency of SF6 data collection;
  • Reducing errors and increasing consistency of emissions calculations through upgrades to the SF6 tracking tools;
  • Ensuring that APS’ contractors will measure accurately when gassing and de-gassing SF6 containing equipment; and
  • Increasing peer reviews to better the quality assurance of field reports

APS will continue the assessments of this program to ensure the continuation of emissions reduction efforts throughout the system.

APS is also planning to implement new, more stringent requirements to further control and reduce SF6 emissions. Starting with the Ocotillo Modernization Project, any new circuit breaker containing SF6 that is installed as part of that project will be limited to a leak rate of less than 0.5 percent as measured by a state-of-the-art SF6 leak rate detection system.

Ash Reuse

APS supports the reuse of its coal ash to help reduce our environmental footprint, while adding to the bottom line. Coal ash is a waste stream resulting from the burning of coal. Ash that is not reused is landfilled on site. APS sells much of its coal ash for use in concrete and concrete-related products. Concrete manufacturers use coal ash as a direct substitute for cement in the production of their products, reducing the amount of cement needed, which in turn eliminates the need to produce the cement, significantly reducing energy consumption. The reduced energy consumption directly correlates to a reduction in greenhouse gas emissions.

The Cholla Power Plant sells approximately 81 percent of its total ash production for reuse. Because of its remote location, the Four Corners Power Plant has a more limited market for ash reuse, selling about 40 percent in 2016. Collectively, between Cholla and Four Corners, APS generated 1,104,205 tons of coal ash in 2016 and sold 537,402 tons, representing 49 percent of the total amount produced. The amount of coal ash sold correlates to a reduction in carbon emissions of 322,441 metric tons in 2016.


In November 2016, Maricopa County adopted new rules that set lower standards for emissions of ozone precursors. APS participated in the rulemaking process and is taking the proper steps to ensure compliance with these new rules.