Heat, Bills, and What Has Not Been Studied

Maricopa County recorded 645 heat-related deaths in 2023, a 52 percent increase from the previous record set in 2022.¹ Every year since 2016 has broken the record before it. In July 2023, an average of 13 people died from heat each day. There were 31 consecutive days that summer where the high reached at least 110 degrees, more than any stretch ever recorded in the county's history. Heat is now the 10th leading cause of death in Arizona.¹

That is where things stand before Baccara.

What Data Centers Add

ASU researcher Dr. David Sailor mounted temperature sensors on vehicles and drove around existing Phoenix-area data centers to measure the effect on surrounding air temperature directly. His team documented consistent air temperature increases of 3 to 4 degrees Fahrenheit at least hundreds of yards downwind of the facilities, with one measurement run showing the zone closest to a facility averaging 2.5 degrees warmer than the zone behind it.² These are actual air temperature measurements, not land surface estimates.

The facilities Sailor studied were approximately 30 megawatts. Project Baccara proposes 700 megawatts of gas-fired generation plus two data center buildings totaling roughly 2 million square feet. No equivalent air temperature study has been conducted for a facility at this scale sited near a residential community. No such study is required by any permit in the Baccara record.

A separate analysis published in March 2026 by researchers at the University of Cambridge examined land surface temperatures near more than 6,000 hyperscale data centers globally using two decades of satellite data. It found average land surface temperature increases of 3.6 degrees Fahrenheit after a facility began operations, with some locations showing increases of up to 16.4 degrees.³ That study has not yet been peer-reviewed, and it measures ground surface temperature, not the air temperature people experience. It is noted here for context, not as a precise prediction.

What 18 Gas Turbines Add

The data center is half of what is proposed. The power plant is the other half. Each of the 18 Siemens SGT-750 simple-cycle turbines exhausts at 850 degrees Fahrenheit.⁴ Each moves 371,851 cubic feet of that exhaust per minute through a 72-foot open stack. All 18 run continuously, 24 hours a day, every day of the year.

No thermal impact study exists in the permit record. The Maricopa County Air Quality Department does not assess heat. The city of Surprise formally requested a review of the project's heat impacts. That request is on the city's own website.⁵ No study was submitted. No study was required.

What the Bills Show

The figures below are drawn from seven months of actual APS bills for a West Valley household on the Time-of-Use 4pm-7pm Weekdays with Demand Charge rate plan. No names, addresses, or account numbers are included. The figures are from the bills as issued by APS. August 2025 is excluded due to an air conditioning failure that affected peak usage during that billing period.^✱ The remaining seven months reflect consistent equipment and consistent habits throughout.

The on-peak demand reading in kilowatts is the most direct measure of what temperature does to this household, because it is not affected by seasonal rate changes. From April through November, the peak demand sits between 1.7 and 2.1 kW every month except one. That floor reflects the household's baseline during peak hours: essential equipment left running, everything else off. In July, at an average of 96 degrees, the peak demand jumped to 4.7 kW. The equipment did not change. The habits did not change. The temperature did.

The demand charge is where that matters most financially. Under this rate plan, the charge for the entire month is set by the single highest hour of on-peak energy use. In July, that hour was July 10th from 4pm to 5pm. One hour set a charge of $92.05 that applied to every day of the billing period. From June to July, average temperature increased 7 degrees. The demand kW more than doubled. The demand charge more than doubled. The total bill rose $74.24.

From July to September, average temperature fell 3 degrees. Peak demand returned to 2.0 kW. By November, temperatures were back to April levels and demand was back to 1.9 kW. The same seven months that show the bill climbing show it coming back down the same way it went up.

Research on Phoenix-area residential cooling loads documents an approximately 2 to 3 percent increase in energy use per degree of ambient temperature increase during summer months.² These bills reflect that relationship in practice, and they also show something the research cannot fully capture: how the demand charge amplifies the cost of a single extreme afternoon across the full billing month.

What APS Said, and What Takanock Said

On June 13, 2025, APS filed a rate case with the Arizona Corporation Commission requesting a 15.99 percent overall revenue increase.⁶ For residential customers the requested increase is 16.44 percent. For customers on the Time-of-Use 4pm-7pm Weekdays plan, APS is seeking approximately a 16.6 percent increase in both on-peak and off-peak energy charges per kilowatt-hour.

The rate case filing included this explanation of why the increase is needed, in APS's own language:

Takanock told ABC15 in January 2026 that Project Baccara "will lower retail utility bills for residential customers."⁷

Both statements are in the public record. They say opposite things.

A Note on the Turbines Themselves

There is a documented engineering relationship between ambient temperature and gas turbine output that is worth stating plainly. As ambient air temperature rises above the ISO standard condition of 59 degrees Fahrenheit, gas turbine power output decreases. Published engineering literature puts the reduction at 5 to 10 percent of rated output per 10 degrees Celsius above ISO conditions.⁸ Arizona summer temperatures routinely reach 40 degrees Celsius or higher, which is 25 degrees above ISO.

The practical result is a documented feedback loop. Higher ambient temperatures reduce turbine output. To compensate, the facility burns more fuel to approach its rated capacity. Burning more fuel produces more heat. More heat raises the ambient temperature further. Each step around the loop makes the next one worse. This is not a projection. It is a known property of simple-cycle gas turbines operating above ISO conditions, documented across multiple peer-reviewed engineering studies, and it is most pronounced on the hottest days of an Arizona summer, when the grid is under the most strain and nearby residents are already running their air conditioning at full load.

What Has Not Been Studied

The permit record for Project Baccara contains no thermal impact assessment. The air quality permit covers air emissions only. No other filed permit addresses heat. The city of Surprise, which is not the permitting authority but whose residents live roughly half a mile from the proposed site, formally requested a review of the project's heat impacts on its own public website.⁵ The request is still there. The study is not.

The Maricopa County Planning and Zoning Commission and the Board of Supervisors retain authority over whether this project proceeds. What the record shows is that 18 gas turbines exhausting at 850 degrees Fahrenheit continuously, adjacent to a 2-million-square-foot data center, in a county where heat already kills hundreds of people per year and where seven additional degrees of average temperature drove one household's peak demand charge from $41 to $92 in a single billing period, has not been studied for its heat impact on the surrounding community.

The county still has a vote. Whether the people casting it have reviewed what the record does not contain is a question worth asking before construction begins.