AriSEIA Submits Letter on Mesa BESS Ordinance

City of Mesa
Development Services
55 N. Center Street
Mesa, AZ 85201
 
RE: City of Mesa Draft BESS Ordinance (Section 11-31-37)
 
Council Members, Planning and Zoning Board Members, and Staff,
 
The Arizona Solar Energy Industries Association (AriSEIA) is the State’s solar, storage, and electrification trade association. We are active on energy policy issues at every level of government in Arizona. We have previously engaged on the City of Eloy, Mohave County, City of Buckeye, Town of Chino Valley, Navajo County, Apache County, Town of Gila Bend, City of Surprise, and Yavapai County solar/storage ordinances.
 
Applicability
AriSEIA recommend that Mesa look at the pending Buckeye BESS ordinance as an example. We further recommend significant changes to B(1)(a) and B(2)(b). As written, this ordinance will potentially apply to many commercial and industrial distributed generation projects. 1 MW is much too small, if the ordinance is meant to only apply to utility scale projects. We recommend you not have any size threshold and instead just state that the ordinance applies only to utility-scale BESS projects, such as is seen in Buckeye’s ordinance (Section 3.2.2(1)): “The requirements of this Section shall apply to all utility-scale BESS facilities permitted, installed, or modified after the effective date, excluding general maintenance and repair. Utility-scale BESS facilities constructed or installed prior to the effective date are not required to meet the requirements of this Chapter.” Alternatively, you could state that the ordinance does not apply to distributed generation projects with on-site battery energy storage. If the City feels it is imperative to include a size threshold, we recommend only doing it in B(1) and not B(2). And it should be 5 MW, not 1 MW.
 
Further, the limitation in B(2)(b)(ii) is problematic because it would preclude commercial and industrial customers from participating in any forthcoming virtual power plant programs offered by the utilities to their business customers. Instead of “exclusively,” it should say “primarily.”
 
Additionally, restrictions in B(1)(a) and C(1) to general and heavy industrial are too limited and may actually create a de facto moratorium on BESS within the City of Mesa. Engineers from Arizona utilities, including Salt River Project (SRP), have publicly spoken about the importance BESS technologies play in ensuring continued electrical service in the Valley amid growing demand. SRP expects electricity demands will grow 6% per year for the next decade, compared against the 2% yearly growth seen from 2015-2025.[1] To keep pace with this demand, SRP will have to double—and possibly triple—its capacity. Given those electricity demand needs, it is absolutely critical to leverage a variety of technologies, including BESS. We recommend all industrial, including light industrial, be eligible for BESS.
 
Setbacks
Tying the ordinance to the most recent versions of UL 9540 and National Fire Protection Agency (NFPA) 855 is recommended. Currently, Mesa has a drafted setback of 400 feet in Section F(2)(a).[2] The American Planning Association found the national setback average for BESS-specific setbacks was 50-150 feet from property lines.[3] While the NFPA recommends 100’, we recommend no more than 150’ from the structures (not the property line) based on the Phoenix Regional Standard Operating Procedures Battery Energy Storage Systems policy.[4] Also, the setbacks should be measured from the BESS equipment, not the BESS property line. This would align Mesa’s ordinance with national standards, improve regulatory defensibility, and ensure that safety requirements scale appropriately with actual risk rather than imposing arbitrary limits that could either under- or over-regulate BESS facilities.
 
Additionally, modern BESS projects are subject to new and updated safety standards and codes that have addressed and corrected issues found in earlier system design.  The American Clean Power Association (ACP) provides a helpful FAQ that covers questions about battery safety and air emissions.[5] ACP also has a Claims v. Facts one-pager on battery safety, included again as Attachment A. “It should also be noted that the average emissions rates of equivalent masses of plastics exceed those of batteries.”[6] Additionally, sampling was done by the Environmental Health Division and the U.S. Environmental Protection Agency (EPA) after the Moss Landing incident and “no threat to human health or the surrounding environment” was found.[7] All electricity generation and energy storage creates some amount of risk. However, battery incidents represent only 2% of battery installations.[8] Setbacks for batteries should not be more onerous than setbacks for other energy infrastructure, such as substations. ACP’s model BESS ordinance is included as Attachment B.
 
Noise
Sound restrictions for BESS should not be different than those for other land uses. E(4) requires an initial sound study before the project is developed and G requires a mitigation plan should the noise level exceed the level when there was no development. Alternatively, at the applicant’s election, we recommend capping the decibel level of the project from the nearest residence. In a residence you would have normal conversation at 60 dB, a vacuum at 70-85 dB, an AC unit or TV at 70 dB. AriSEIA recommends the City not require a noise level less than 65 dB from the nearest residence if the ambient noise is below that.
 
BESS Spacing
Any BESS spacing in F(3) should only be 3 ft. The NFPA 855 sets its threshold at 3 feet between individual BESS units. NFPA 855 allows for adjustment upward or downward based on site-specific hazard data, including through written agreements with adjacent property owners, provided that such agreements are reviewed and accepted by the City and supported by the site’s hazard mitigation analysis (HMA). This mechanism allows jurisdictions to maintain safety standards while accommodating site-specific conditions and product design innovations.
 
Mesa’s suggestion to increase cabinet spacing over and above the requirements of the fire code are not without consequences. Projects that require more internal spacing will require more land for development. Consequently, these projects will become bigger in area and be costlier to develop. This will come back to Mesa citizens in the rates they pay for electricity.  
 
(F)(4) requires that all fire access drives and drive aisles within the BESS facility be paved and (F)(6) requires full site screening with opaque walls or fences extending one foot or greater from the top of the equipment. By exceeding NFPA’s safety recommendations, these proposed requirements impose significant costs and potentially jeopardize project feasibility without a commensurate increase in safety. Instead, the ordinance should align these standards with NFPA 855 and (1) allow drive aisles to be made of aggregate all-weather surfacing and (2) only require partitions to be one foot higher than BESS units.
 
Undergrounding
In F(8), the City appears to require undergrounding of distribution and transmission lines. AriSEIA recommends that whether lines are undergrounded or not be left to the BESS Facility, the utility, and the Arizona Corporation Commission’s (ACC) Power Plant and Line Siting Committee (if applicable), as the ACC has a policy on undergrounding that disfavors it, as it can be excessively costly.[9]
 
Waiver Provision
The ordinance should include a waiver provision in the event a project proposal conflicts with some component of the ordinance, but is otherwise an ideal site. The City of Eloy Solar and BESS Ordinance includes such a provision.[10] We recommend adding language such as that included in 21-3-1.39(B) of Eloy’s ordinance. A waiver provision gives the city the flexibility when special circumstances and safety demand.
  
Other
 
Additionally, there is an error in the nameplate capacity definition. We recommend an updated definition such as, “NAMEPLATE CAPACITY: The maximum rated power output that a battery energy storage system (BESS) or facility can discharge or receive under specific conditions designated by the manufacturer. It is also referred to as rated capacity or peak capacity, and is expressed in megawatts (MW) or kilowatts (kW) for power. The associated energy capacity, sometimes referred to as nameplate energy capacity, represents the total amount of energy the system can store or deliver over time, expressed in megawatt-hours (MWh) or kilowatt-hours (kWh).”
 
As discussed above, the NFPA 855 provides recognized industry best practices for BESS. Incorporating NFPA 855 by reference into this ordinance will provide Mesa with clear, nationally recognized metrics on maximum system capacity, hazard mitigation, emergency response, and decommissioning.
NFPA 855 requires the following submittals and by incorporating NFPA 855, Mesa will be requiring each of these:

• Hazard Mitigation Analysis (HMA);
• Emergency Response Plan;
• Details of all safety systems, including;
  • UL 1973 – for battery modules and components;
  • UL 9540 – for integrated BESS systems;
  • UL 9540A – for fire propagation testing to evaluate thermal runaway risk; and
    • Results of UL 9540A or equivalent testing

Thank you for your time and consideration and we look forward to continuing to engage with the
City on this ordinance as the stakeholder process progresses.
 
Respectfully,
Autumn Johnson
Executive Director
AriSEIA 
(520) 240-4757
[email protected]

[1] Pinal County, Board of Supervisors meeting, Sept. 10, 2025, available here https://pinalcountyaz.new.swagit.com/videos/355087?ts=230.

[2] This setback is in addition to further setbacks between the BESS installation and its own project boundary.

[3] American Planning Association, Zoning Practice, P.10 (Mar. 2024), available here https://planning-org-uploaded-
media.s3.amazonaws.com/publication/download_pdf/Zoning-Practice-2024-03.pdf

[4] City of Phoenix, Battery Energy Storage Systems, April 2023, available here https://www.phoenix.gov/firesite/Documents/205.20A%20Battery%20Energy%20Storage%20Systems.pdf.

[5] American Clean Power Association, Energy Storage: Safety FAQ, available here https://cleanpower.org/wp-content/uploads/gateway/2023/07/ACP-ES-Product-4-BESS-Safety-FAQs-230724.pdf.

[6] Consolidated Edison and NYSERDA, Considerations for ESS Fire Safety, Feb. 9, 2017, at iii, available here https://www.nyserda.ny.gov/-/media/Project/Nyserda/files/Publications/Research/Energy-Storage/20170118-ConEd-NYSERDA-Battery-Testing-Report.pdf.

[7] County of Monterey, Air Quality Testing Information and Process During Moss Landing Fire Incident, Sept. 30, 2022, available here https://www.countyofmonterey.gov/Home/Components/News/News/9345/1336.

[8] California Public Utility Commission, Energy Storage Procurement Study: Safety Best Practices, 2023, available here https://www.cpuc.ca.gov/-/media/cpuc-website/divisions/energy-division/documents/energy-storage/2023-05-31_lumen_energy-storage-procurement-study-report-attf.pdf.

[9] Arizona Corporation Commission, Decision No. 79140, P.3, L.2-6, Oct. 4, 2023, available here https://docket.images.azcc.gov/0000209995.pdf?i=1760388397879.

[10] Eloy Ordinance, 21-3-1.39, available here https://codelibrary.amlegal.com/codes/eloyaz/latest/eloy_az/0-0-0-9381.

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