Delivering safe, reliable, affordable energy to our customers requires a balanced energy mix, something APS has achieved with a combination of traditional and renewable sources of energy. As we continue to provide our customers with increasingly cleaner energy, that mix remains balanced. But it is changing.
By closing coal units, modernizing natural gas plants, deploying renewable energy and energy efficiency, and operating Palo Verde Nuclear Generating Station, the country’s largest source of carbon-free energy, we are reducing our carbon footprint. APS is proud to be a leader in Arizona with an energy transition that will fulfill our mission to create a sustainable energy future for the state. In 2015, 47 percent of our energy came from carbon-free resources, and we expect renewable energy and energy efficiency to meet over 50 percent of our energy growth through 2031.
Our efforts to reduce our carbon footprint are not limited to energy generation. We also have increased the efficiency of our facilities and transportation fleet, lowering our own energy usage and reducing vehicle emissions. Through these combined efforts, we avoided 3.8 million metric tons of carbon dioxide emissions that otherwise would have been emitted in 2015. This is equivalent to removing over 800,000 automobiles from the road.