We have undertaken a number of initiatives to address emissions related to climate change, including renewable energy procurement and development, promotion of programs and rates that promote 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 Climate Survey since 2006. In 2016, we had our Scope 1, 2, and 3 greenhouse gas emissions third-party verified. In addition to these actions, 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 actively working to measure and reduce SF6 emissions since voluntarily joining EPA’s SF6 Emission Reduction Partnership for Electric Power Systems in 2004 to identify and implement cost effective solutions for meaningful emissions reductions. 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.

Beginning in 2011, EPA implemented the Greenhouse Gas Reporting Rule, which requires APS to report total SF6 emissions on an annual basis. APS’s on-going reduction efforts include not only reporting emissions, but also fixing or replacing specific current breakers that have been identified as leaking SF6. Of the breakers identified as leaking, SF6 emissions have been reduced by 42.4 percent over a three-year period, from 2,180 pounds in 2011 to 1,255 pounds in 2014. APS remains committed to making continued reductions through a robust corrective action and self-assessment program.

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 that would otherwise occur.

The Cholla Power Plant sells approximately 72 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 one third in 2015. Collectively, between Cholla and Four Corners, APS generated 1,789,561 tons of coal ash in 2015 and recycled 788,883 tons, representing 44% of the total amount produced. The amount of coal ash recycled correlates to a reduction in carbon emissions of 474,759 metric tons in 2015.