Big natural gas plant expansion in the works for SRP; environmentalists question move

Environmentalists say the plan moves SRP in the opposite direction of its climate goals, but SRP officials contend it will help its renewable efforts.
Ryan Randazzo
Arizona Republic

Salt River Project is planning a nearly $1 billion expansion at a Coolidge natural-gas burning power plant that officials say is necessary to maintain reliability on the Phoenix power grid.

The Coolidge Generating Station would more than double, with 16 new generators added through the expansion. The quick starting generators can react to fluctuations on the grid, including intermittent power from renewable sources like solar and wind.

Environmentalists say the investment in gas plants moves the utility in the opposite direction of its climate goals, but SRP officials said the gas plants are needed to help integrate more intermittent solar and wind on the grid.

The Power Committee of the SRP board approved the deal on Tuesday, with a cap on expenses at $953 million, which officials said was in case the project costs more than the $830 million estimate. It will need an affirmative vote from the full board to proceed.

"The primary driver is the significant near-term growth we are seeing," said Grant Smedley, director of resource planning, acquisition and development for the utility.

SRP is pursuing additional solar, battery and even a new wind project, he said, and the company still plans to hit its target of reducing carbon emissions 65% in 2035 and by 90% in 2050 when compared with 2005 levels.

SRP also plans to add 2,025 megawatts of new solar from large power plants by 2025, plus substantial capacity from large, utility-scale batteries. A megawatt of power is about enough electricity to supply 250 homes at once.

"We are pursuing an all-of-the-above energy strategy," Smedley said.

In addition, California has faced energy constraints the past two summers, prompting concerns about supply throughout the West.

"It really serves as additional motivation for us to pursue this," Smedley said of California's supply issues. "What you see from that is increased risk we would have relying on (buying energy on) the market for those peak summer afternoons. For us, we'd like to have our own resources that we can count on that we can build to serve our customers' needs."

Expansion would add 820 megawatts

The 615-megawatt Coolidge power plant will grow significantly under the plan. It currently has 12 generators on site, and the capacity to power about 150,000 homes when running at full capacity.

The expansion would add another 820 megawatts, or enough to power about 200,000 homes when running at full capacity.

Salt River Project's Coolidge Generating Station in Coolidge, Ariz.

SRP says the expansion is needed because the Phoenix area is growing, with more homes and businesses, including large industrial operations, according to SRP. The public utility also cites power constraints across the West as a need for additional power.

The gas units would only operate on the hottest hours of summer or other times when energy demand is highest, and would therefore make a "relatively small contribution" to overall carbon emissions, according to SRP.

Smedley said it is cheaper to add the gas units rather than solar plus storage to meet the demand on the hottest summer afternoons.

SRP's plan is for the first eight units to be running in summer of 2024 and second eight in summer 2025.

After an emergency declaration last month that temporarily lifted air-quality rules, California officials recently announced that the state would add five new natural-gas plants, totaling 150 megawatts of capacity, to help deal with short-term energy needs.

Sierra Club: 'Very disturbing' decision

SRP gave a preview of the plans to interested stakeholders Monday, and Sierra Club's director of the Grand Canyon Chapter, Sandy Bahr, said the proposal is troubling.

"It is very disturbing that SRP is doubling down on gas, especially in light of the recent Intergovernmental Panel on Climate Change report and the immediacy of the need to act on climate and reduce methane emissions — a powerful greenhouse gas," Bahr said Monday in an email to The Arizona Republic. 

She said SRP previously indicated that by extending the life of its Coronado Generating Station coal-burning plant in eastern Arizona, the utility could avoid building additional gas power plants.

"Now they are proposing 820 Megawatts! That is a lot of gas and a lot of emissions and absolutely not the direction they should be headed," Bahr said. "Now is a time when they should be increasing their renewable commitment even more coupled with deep energy efficiency investments, not more polluting gas."

She said Sierra Club also is concerned about the emissions from the gas plant that will contribute to ozone pollution.

Arizona Public Service Co., which also provides electricity in the Phoenix area, also recently made a large investment in natural gas with an expansion at the Ocotillo Power Plant in Tempe. Sierra Club likewise opposed that expansion and investment in additional natural-gas infrastructure.

Reach reporter Ryan Randazzo at or 602-444-4331. Follow him on Twitter @UtilityReporter.