City of Mesa
20 E. Main Street
Mesa, AZ 85201
 
RE: Comments on Item 7 of the December 1 Agenda
 
Dear Mayor and Councilmembers,
 
On behalf of the Arizona Solar Energy Industries Association (AriSEIA), I urge you to reject the proposed 1,000 foot setback for battery energy storage systems (BESS) in Agenda Item 7. AriSEIA is Arizona’s solar, storage, and electrification trade association, and we previously submitted detailed BESS comments to the City in our October 15, 2025 letter.
 
A 1,000 foot setback is arbitrary, unsupported by data or national standards, and would function as a de facto moratorium on BESS in Mesa at the very moment when the region is facing record peak demand and rapidly rising electricity bills. Arizona’s three largest utilities have all set new peak demand records in recent summers, and Salt River Project expects continued significant load growth over the coming decade.[1] These conditions require more flexible, dispatchable resources, not fewer.
 
When this ordinance was before the Planning and Zoning Board, the 400 foot setback already under consideration was too large. Every member of the public who testified spoke against it and urged you to follow national standards instead. Yet, staff has proposed increasing the setback to 1,000 feet. That change moves Mesa even further away from evidence based practice.
 
National guidance and emerging practice in other jurisdictions point in a very different direction. The American Planning Association’s Zoning Practice review of BESS ordinances found that BESS specific setbacks in adopted codes are typically in the range of 50 to 150 feet from property lines.[2]
 
In addition, The National Fire Protection Association (NFPA) 855, the national consensus standard for installation of stationary energy storage, and related guidance used by fire professionals recommend a 100 foot separation between large outdoor BESS and nearby buildings or public ways to manage worst case thermal and blast scenarios.[3] Many jurisdictions address BESS separation primarily through adoption of NFPA 855 and the International Fire Code, combined with project specific review by the fire authority that can consider technology type, enclosure design, fire barriers, and egress.
 
Maricopa County provides a good example of this approach. County staff initially proposed a 500 foot separation between BESS and existing off site residences, but after hearing from fire experts and stakeholders, the Planning and Zoning Commission advanced an ordinance that dropped the 500 foot residential separation.[4] In other words, the County chose not to create a second, much larger layer of BESS specific zoning setbacks on top of the fire code.
 
By contrast, a 1,000 foot setback from BESS equipment to homes, churches, and similar uses in Mesa would:
 
• Push viable sites so far from load that projects become infeasible or uneconomic.
• Single out BESS for treatment that is far more restrictive than other critical energy infrastructure, such as substations.
• Effectively ban standalone BESS projects in most of the City while still allowing other, higher risk facilities at much closer distances.
 
Mesa does not need to reinvent the wheel. There are several defensible paths available to the Council that are protective of public safety and aligned with best practice:
 
1.      Follow the Maricopa County model and rely primarily on the fire code.
Mesa can remove the BESS specific separation requirement from the zoning text and allow the adopted fire code, which incorporates NFPA 855 requirements and related standards, to govern separation distances, fire protection features, and emergency response planning, with project specific review by Mesa Fire and Medical.
 
2.      If the Council decides to retain a numeric setback, it should align with national standards.
A maximum of 100 feet from BESS equipment to property lines is consistent with NFPA 855 guidance and with conditions used in Maricopa County approvals. This distance should always be measured from the BESS structure itself and not from the property line of the BESS parcel.
 
3.      If the Council wants an additional margin of comfort, it should not exceed 150 feet.
Buckeye has already adopted a 150 foot standard, based on the Phoenix Regional Standard Operating Procedures for BESS and NFPA guidance.[5] A 150 foot limit would still be conservative relative to many jurisdictions yet it would remain within the range documented by the American Planning Association.
 
Adopting a 1,000 foot setback would place Mesa well outside the mainstream of BESS regulation, chill investment in energy storage, and worsen the very reliability and affordability challenges your residents are already facing. A more measured, standards based approach is both safer and more practical.
 
For these reasons, AriSEIA respectfully asks the Council to reject the proposed 1,000 foot setback in Agenda Item 7, remove the BESS specific separation requirement from the zoning text or, at most, replace it with a setback no greater than 100 to 150 feet that is tied to NFPA 855 and Mesa’s adopted fire code.
 
Thank you for your consideration and for your continued work on policies that keep Mesa safe, reliable, and affordable while enabling clean energy investment.
 
Respectfully,
/s/ Autumn T. 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.
Utility Dive. “Arizona utilities hit new peak demand during extreme heat.” July 2023.
Available at: https://www.utilitydive.com/news/arizona-utilities-peak-demand-heat-wave/686198/

[2] American Planning Association. Zoning Practice: Regulating Battery Energy Storage Systems. March 2024.
Available at: https://planning-org-uploaded-media.s3.amazonaws.com/publication/download_pdf/Zoning-Practice-2024-03.pdf

[3] National Fire Protection Association. NFPA 855: Standard for the Installation of Stationary Energy Storage Systems. 2023 edition.
UL. UL 9540A Test Method for Evaluating Thermal Runaway Fire Propagation in Battery Energy Storage Systems.

[4] Maricopa County Planning and Zoning Commission. Public Hearing on Text Amendment TA2024001 (Battery Energy Storage Systems). November 6, 2024.

[5] City of Buckeye. Zoning Code, Article 3: Use Regulations. Battery Energy Storage Systems standards adopted October 21, 2025.

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.