Public Safety Tower Backup Power
7.68 hrs rated runtime at 1 kW | Zero-glitch transfer — no switching transient | 26 dry contacts for SCADA integration | 3-year payback | Deployed across public safety networks nationwide
The FCC requires covered 911 service providers to maintain backup power. FirstNet established an 8-hour runtime benchmark for Band 14 network sites. The National Council of Statewide Interoperability Coordinators (NCSWIC) publishes Statewide Communication Interoperability Plans (SCIPs) that increasingly include backup power specifications. Every one of these standards points to the same gap: most public safety tower sites are still running backup systems designed for 5 to 15 minutes of bridge power.
Evoltix’s Zero-Glitch Power Module (ZPM) is a power intelligence system purpose-built for the sites that those standards are trying to protect. It is not just a UPS. It is what public safety agencies deploy when a UPS is no longer adequate for what their network demands.
What P25 and 911 Networks Actually Require from Backup Power
Project 25 (P25) is the suite of standards established by APCO International that governs digital radio interoperability for public safety communications. A P25-compliant network, whether Phase 1 FDMA or Phase 2 TDMA, requires tower sites, repeater sites, and backhaul nodes that stay online when the grid fails. The backup power system at each site is a direct dependency of P25 network availability.
Three technical realities define what an adequate backup power system for a P25 or 911 network site must deliver:
P25 radios, 911 dispatch consoles, and CAD (Computer-Aided Dispatch) systems are zero-tolerance for power interruptions. A line-interactive UPS with a switching delay, even 4 to 8 milliseconds, can cause a radio to drop off the network or a dispatch console to reboot. The ZPM uses online double conversion architecture: power is continuously converted through the battery, meaning the connected load never experiences a switching transient when transitioning from grid to battery. This is the same principle behind the product’s name — Zero-Glitch Power Module.
P25 and 911 sites face the highest demand for uptime during major incidents — the same events that cause extended grid outages. FEMA’s post-disaster data consistently shows that utility restoration at rural and suburban tower sites lags behind incident resolution timelines. The FirstNet Band 14 network established an 8-hour backup runtime benchmark for its sites. Most legacy UPS systems at tower sites provide 15 to 30 minutes. The ZPM 1 at a typical 1 to 2 kW P25 site load provides 3.84 to 7.68 hours of rated runtime, which is well above the FirstNet benchmark and able to sustain a site through most regional grid events without generator support.
The vast majority of P25 tower sites are unmanned. When a battery fails silently at 2am during a storm, the first sign is a dark site, by which point the communications team is already in the middle of an incident response. Evoltix’s IntelliCore platform gives state network managers and communications center staff real-time visibility into battery state of charge, grid status, power conversion health, and load, and sends automated alarms via dry contacts and dashboard alerts when conditions change. State DOT and emergency management network teams who have deployed the ZPM describe the shift from reactive dispatch to proactive remote management as one of the most operationally significant changes they have made to their infrastructure programs.
Where Legacy UPS Systems Are Failing Public Safety Networks
The public safety agencies that have upgraded to the ZPM did not do it because their old UPS systems were broken. They did it because the old systems were no longer adequate for what a modern P25 or 911 network demands.
- Runtime gap: A standard UPS at a 2 kW tower load provides approximately 15 to 30 minutes of backup. The ZPM 1 at the same load provides 3.84 hours. That is not a marginal improvement, but is the difference between a site that stays online through a major storm and one that goes dark before the incident peaks.
- Silent battery failure: VRLA lead-acid batteries, which are standard in most commercial UPS systems, degrade without warning. The first sign of a failed battery is often a dark P25 site during the event you needed it to survive. LFP batteries in the ZPM degrade predictably and are continuously monitored by IntelliCore.
- No visibility between failures: Legacy UPS systems provide limited remote insight into battery condition, grid status, or load. Communications teams find out about a problem when the site stops responding — not in time to prevent it.
- SCADA integration gaps: Many public safety networks operate behind OT-secured or air-gapped architectures with SCADA monitoring infrastructure. A standard UPS provides no mappable dry contacts. The ZPM provides 26.
- Battery replacement cycles compound across a network: Lead-acid batteries require replacement every 3 to 5 years. A SWIC managing a statewide P25 network with 40, 80, or 150 tower sites is looking at a recurring battery replacement program that consumes staff time, budget, and truck rolls indefinitely. The ZPM’s LFP chemistry is rated for up to 15 years.
ZPM Backup Runtime at Typical P25 Site Loads
Highlighted rows (green) = the 1 to 4.5 kW range typical of P25 tower sites, conventional repeater sites, and 911 PSAP feed sites. Source: Evoltix ZPM spec insert 02.26_01. All runtime figures are rated values at 100% depth of discharge.
| Critical Load | Amps @ 48VDC | ZPM 1 (up to 4.5 kW) | ZPM 2 (4.5–9 kW) | ZPM 3* (9–13.5 kW) |
|---|---|---|---|---|
| 0.5 kW | 10.42A | 15.36 hrs | 30.72 hrs | 43.08 hrs |
| 1 kW | 20.83A | 7.68 hrs | 15.36 hrs | 23.04 hrs |
| 1.5 kW | 31.25A | 5.12 hrs | 10.24 hrs | 15.36 hrs |
| 2 kW | 41.67A | 3.84 hrs | 7.68 hrs | 11.52 hrs |
| 2.5 kW | 52.08A | 3.07 hrs | 6.14 hrs | 9.22 hrs |
| 3 kW | 62.50A | 2.56 hrs | 5.12 hrs | 7.68 hrs |
| 3.5 kW | 72.92A | 2.19 hrs | 4.39 hrs | 6.58 hrs |
| 4 kW | 83.33A | 1.92 hrs | 3.84 hrs | 5.76 hrs |
| 4.5 kW | 93.75A | 1.71 hrs | 3.41 hrs | 5.12 hrs |
| 5 kW | 104.17A | — | 3.07 hrs | 4.61 hrs |
| 6 kW | 125.00A | — | 2.56 hrs | 3.84 hrs |
| 7 kW | 145.83A | — | 2.19 hrs | 3.29 hrs |
| 8 kW | 166.67A | — | 1.92 hrs | 2.88 hrs |
| 9 kW | 187.50A | — | 1.71 hrs | 2.56 hrs |
| 13.5 kW | 281.25A | — | — | 1.71 hrs |
*ZPM 3 in development. Actual runtime varies by load profile and operating conditions. For simulcast networks and high-load P25 Phase 2 sites, consult an Evoltix application specialist for a site-specific runtime analysis.
How the Evoltix ZPM is Built for Public Safety Infrastructure
The ZPM ships as a single rack-mount unit (19″ x 24″ x 84″, 850 lbs fully configured) with batteries mounted, wired, and tested at the factory. A typical two-person crew can complete installation without special tooling. For a SWIC or state network manager specifying backup power across a fleet of sites, the standardized SKU and modular design are operationally significant — one specification covers the network, and deployment is repeatable.
Online double conversion -- zero-glitch power protection
The ZPM’s online double conversion architecture means the connected P25 load never experiences a switching transient. Power is continuously converted through the battery bank, and the output to the site is always clean, conditioned AC power regardless of grid conditions. For P25 Phase 2 TDMA infrastructure where timing is critical, and for simulcast networks where all sites must remain synchronized, this architecture eliminates the power-transition failure mode entirely.
IntelliCore: Remote power intelligence for state network teams
Every ZPM includes IntelliCore, Evoltix’s remote power monitoring and management platform. State network managers and communications center staff get real-time visibility into battery state of charge, grid status, power conversion health, and load from a single dashboard. Automated alarms trigger on configurable conditions — grid loss, battery threshold, load anomaly — and are delivered to your communications center or state EOC via dry contact outputs and IntelliCore notifications. Advanced diagnostics surface battery degradation and system anomalies before they become site failures.
26 dry contacts for SCADA and OT-secured network integration
The ZPM’s 26 mappable dry contact alarms provide alarm and status outputs compatible with existing SCADA and OT monitoring infrastructure. Core ZPM and IntelliCore functionality does not require internet connectivity — dry contact outputs function independently of network availability. For state P25 networks operating behind OT-secured or air-gapped architectures, this is the correct integration model.
Clean, maintenance-free LFP batteries, no ventilation required
Lithium-iron phosphate batteries require no ventilation for off-gassing, simplifying shelter and enclosure design for existing P25 sites. Battery condition is continuously monitored and degrades predictably. The 15-year rated service life eliminates the recurring battery replacement cycle that currently drives a significant portion of P25 tower maintenance costs for state network programs.
A specification that scales across a statewide network
For SWICs and state network managers specifying backup power across a statewide P25 network, the ZPM’s standardized rack-mount form factor, modular design, and consistent SKU structure means one procurement specification covers every site in the network. The ZPM 1 handles typical P25 and 911 site loads up to 4.5 kW. The ZPM 2 covers higher-load sites and 5G-augmented infrastructure up to 9 kW. State DOT networks that have deployed the ZPM report that the standardization benefit — reduced training, consistent spare parts, repeatable installation — is a material operational advantage over the fragmented UPS landscape it replaces.
Grant Funding for Public Safety Backup Power Upgrades
Public safety agencies upgrading tower backup power systems may be eligible for federal funding through several programs. The ZPM’s documented runtime, monitoring capability, and 15-year battery service life directly support the hardening and resilience objectives these programs fund.
Talk to an Evoltix Application Specialist
Frequently Asked Questions
What is a power intelligence system, and how is it different from a UPS for a P25 or 911 site?
A power intelligence system combines backup power, DC distribution, energy storage management, remote monitoring, automated alarms, and predictive diagnostics into a single preintegrated unit — purpose-built for tower sites. A UPS provides backup AC power for a limited duration, typically 5 to 15 minutes at tower site loads. Evoltix’s ZPM is a power intelligence system. For P25 and 911 sites, it delivers online double conversion architecture (zero transfer time), 2+ hours of rated runtime at typical loads, 26 dry contact alarms for SCADA integration, and real-time visibility through IntelliCore — all from a single rack-mount unit that ships with batteries installed.
Does the ZPM meet the 8-hour runtime benchmark established for FirstNet Band 14 sites?
At 1 kW of critical load — typical for smaller P25 repeater and conventional sites — the ZPM 1 provides 7.68 hours of rated runtime. Sites drawing 1.5 kW run for 5.12 hours. The ZPM 1 meets or approaches the 8-hour FirstNet benchmark across the lower end of typical P25 site load profiles. For sites with higher loads, the ZPM 2 provides proportionally greater runtime. An Evoltix application specialist can confirm the right model and configuration for your specific site load profile.
Can the ZPM integrate with an OT-secured or air-gapped P25 network?
Yes. The ZPM’s 26 mappable dry contact alarms provide alarm and status outputs that function independently of internet connectivity. Core ZPM operations do not require network access. IntelliCore remote monitoring is available when network connectivity is present, and dry contact outputs integrate with existing SCADA and OT monitoring infrastructure regardless of network security posture. This is the correct integration model for state P25 networks operating behind air-gapped or OT-secured architectures.
How does the ZPM compare to a standard UPS for a public safety tower?
A standard UPS provides backed-up AC power for 5 to 15 minutes at typical tower site loads. The ZPM provides online double conversion with zero transfer time, 2+ hours of rated runtime at typical P25 loads, AC and DC power distribution from one unit, 26 dry contact alarms, real-time remote monitoring through IntelliCore, a 15-year battery lifespan, and no ventilation requirement — from a single preintegrated rack-mount unit. The ZPM is not a better UPS. It is the power intelligence system that replaces the need for a UPS at P25 and 911 sites that cannot afford the failure modes of legacy backup power.