Ocotillo FAQs

Why is APS proposing this project?
This is a major modernization project to create a cleaner-running, more efficient Ocotillo plant. We are updating the plant with advanced, more responsive generating technology and will remove two 1960s-era steam generators.
The upgraded plant will help us provide many economic and environmental benefits, maintain reliable electrical service and provide quick-start, flexible generation so that we can integrate growing solar energy resources and meet customers' changing energy needs.
What are the details of the proposal?
The generators, which were built in 1960, the adjacent cooling towers and large oil storage tanks will be removed as part of the project. Two existing 55-MW generators built in the early 1970s will remain.

APS is installing five 102-megawatt (MW) units, still powered by natural gas. The units will be more fuel-efficient, decrease water-use rates and reduce emission rates compared to the two old generators planned for removal.
What is the project timeline?
Construction on the new units has begun and is planned to be completed by summer 2019. Removal of the old units would begin in 2020.
Why is APS adding new generation?
A combination of customer growth, increased electricity demand and expiring power contracts over the next decade is driving the planned new generation. We project customer energy demand to grow 2% annually in the next decade as Arizona's population continues to increase.
We will need an estimated 5,000 MW of additional energy resources through 2032 to meet the demand. While this project would increase our generating capacity at Ocotillo, most of the needed energy will come from third-party providers. 

Why upgrade the Ocotillo plant?
The Ocotillo plant is critical to maintain service reliability in the Phoenix metro area because of its location. We can also improve an existing plant without changing its overall footprint. The planned new units are also much more responsive – they can start up and begin delivering electricity in less than six minutes and reach full power in less than 10 minutes. The old units can take six hours or more just to start.
What economic benefits will the project provide?
Overall, the modernization project will provide several economic and environmental benefits.
It will create local jobs – we expect the project to require an average of more than 100 jobs during construction. (The plant currently has about 30 employees.)
Total property taxes for the upgraded plant would increase to $8 million by the fifth year of operation. APS currently pays about $600,000 in total property taxes for Ocotillo.
For the City of Tempe, the plant currently generates about $60,000 in property taxes. That is estimated to increase to $850,000 by the fifth year of service.
The project will reduce the plant’s visibility from several locations. The new units will have stacks about half the size of the existing ones, which are 178 feet tall.
The units will operate more efficiently with decreased water-use rates and reduced air emission rates compared to the existing steam generators.
What will the environmental benefits be?
Replacing the obsolete steam generators with much newer, proven, cleaner technology will greatly improve the plant’s efficiency. The new units will decrease the plant's water-use and emission rates. They will also improve the plant's overall noise conditions. 

Will the plant be noisier?
The project would nearly double the plant’s generating capacity without increasing maximum noise levels. The current units are loudest during start-up, which can take hours to complete. The proposed units would take just minutes to start up, meaning their maximum noise levels wouldn’t last nearly as long.
Comparison: When standing next to the units during normal operation, they would sound about the same as traffic you hear inside your car while city driving.
How will the project impact water use?
The new units operate more efficiently, so water-use rates at the plant are expected to decrease.  The cooling system to be installed for the units is planned to use about 140 gallons per megawatt-hour. That's considerably less than the 1,000 gallons per megawatt-hour that the existing steam generators use with their aging technology. 
Why is APS adding natural gas generation?
A balanced resource mix is essential to reliable electricity service. As we integrate variable energy from renewables such as solar, APS must be able to start and stop generators quickly to meet customer demand throughout the day. Upgrading Ocotillo with quick-start, gas-fired combustion turbines will give APS the flexibility to respond to customer demand and provide a seamless power supply 24/7 while supporting renewable energy resources.
How will this project improve electricity reliability in the Phoenix metro area?
There are a number of technical reasons that this project would address in supporting reliability and maintaining balance on the grid for the entire state. Ocotillo’s central location provides generation and transmission advantages, such as meeting peak summer demand with localized generation, that other locations outside the Phoenix metro area cannot match.
Which government agencies must approve the project?
The Arizona Corporation Commission, Maricopa County Air Quality Department, the U.S. Environmental Protection Agency, City of Tempe and Arizona Department of Water Resources have been involved in the approval process for the plant.

How tall will the new structures be?
The plant currently has four 178-foot stacks, while the upgraded plant will have five stacks about half as tall. This would significantly reduce the plant’s visibility from several locations.
How will this project affect ASU?
APS has enjoyed a long working relationship with ASU, particularly in regard to Ocotillo and the university’s surrounding properties. The project is not increasing the plant’s physical footprint and will reduce the plant’s overall visibility from many nearby locations after the steam generators are removed.
How can I get involved in the project?
APS is committed to a transparent public process. Information about the project is available on azenergyfuture.com/ocotillo. In addition, we held a public open house to provide information and take comment, and we have participated in public forums for government agencies that provide oversight of various project components.