UniFi PoE budget planning is one of the most overlooked steps in commercial surveillance design — and PoE budget failures are one of the most common causes of post-installation problems in commercial UniFi deployments. A camera that won’t power on, an access point that reboots under load, or a door reader that drops offline during peak hours — all trace back to under-specified PoE infrastructure. This guide gives network engineers and facilities IT teams the tools to size PoE correctly before installation day.

1. PoE Standards Explained

Power over Ethernet delivers DC power to devices through standard Ethernet cabling. Three IEEE standards govern how much power is available per port:

Standards reference: IEEE 802.3at (PoE+) standard  |  UniFi switch specifications — ui.com

2. UniFi Device Power Draws (at PSE)

Use these values when calculating total PoE budget requirements. Values represent maximum power draw (worst-case planning):

Cameras

Access Points & Access Control

UniFi PoE budget planning requires knowing exactly how much each switch model can deliver — the table below is the foundation of every commercial PoE architecture design.

3. UniFi Switch PoE Budgets

The UniFi PoE budget planning calculation method below eliminates guesswork and prevents the brownout failures that plague under-designed commercial deployments.

4. PoE Budget Calculation Method

Follow this method for every commercial deployment:

1. List all PoE devices — cameras, APs, access readers, access hubs, VoIP phones, doorbells
2. Record max power draw per device — use the values from this guide or Ubiquiti’s techspecs page
3. Calculate total maximum draw: sum of all device max powers
4. Apply a 20% safety margin: total max draw ÷ 0.80 = minimum switch PoE budget required
5. Select a switch whose PoE budget exceeds this number — with room for planned future additions
6. Verify per-port standard: ensure PoE+ devices connect to PoE+ ports; PoE-only switches cannot power PoE+ devices

5. Real-World Planning Examples

Example A — Warehouse Perimeter (20 cameras)

Example B — Office Building (cameras + APs + access control)

UniFi PoE budget planning extends to every IDF closet in a multi-floor facility — not just the total building load.

6. IDF/MDF PoE Planning

Commercial buildings distribute network infrastructure across MDF (Main Distribution Frame) and IDF (Intermediate Distribution Frame) closets per floor or zone. PoE planning must account for this topology:

• Size each IDF switch independently — calculate PoE budget for devices connected to each IDF switch, not the total building
• Fiber uplinks between IDF and MDF carry data only, not PoE — devices receive power from their local IDF switch
• Avoid over-subscribing single IDF switches — plan to split devices across multiple switches if a single floor exceeds 70% of one switch’s PoE budget
• AC power to IDF closets — each IDF switch requires local AC power. Verify electrical capacity in each closet, especially in older commercial buildings where closets may have limited circuits

Brownout failure prevention is the most operationally critical outcome of correct UniFi PoE budget planning — cameras and APs that drop during an incident are worse than no cameras at all.

7. Avoiding Brownout Failures

A PoE brownout occurs when total device power draw approaches or exceeds the switch’s PoE budget. Symptoms include cameras randomly dropping offline, APs resetting under high client load (when radio power draw peaks), and access readers intermittently failing to unlock doors.

Prevention strategies used by 2M Technology on every commercial deployment:

• Never exceed 80% of total PoE budget: leave 20% headroom for startup surges and planned additions
• Use UniFi’s PoE monitoring: UniFi Network Controller shows per-port and total PoE consumption in real time — review after installation and quarterly
• Stagger PoE device startup: after a power outage, simultaneous restart of all cameras can surge past the switch budget momentarily — UniFi switches handle this with PoE port priority settings
• Set PoE port priority in UniFi: assign access control readers and critical cameras higher PoE priority than overview cameras — ensures critical devices power on first if budget is approached

8. Long Runs & Power Loss

PoE power delivery efficiency decreases with cable length and cable quality:

• Maximum run length: 100 meters (328 ft) per IEEE 802.3 specification for both data and PoE
• Cat5e vs. Cat6: Cat6’s lower resistance provides better power delivery efficiency on long runs — use Cat6 for all runs exceeding 60 meters and all PoE+ devices
• Avoid splitters and couplers: Ethernet couplers, inline splitters, and low-quality patch cables introduce resistance that reduces available power at the device end
• PoE extenders: For runs beyond 100 meters, UniFi and third-party PoE extenders repeat both data and power — useful for distant parking lot cameras or fence line coverage without additional IDF infrastructure

UniFi PoE Budget Planning — Switch Selection Quick Reference

The most expensive UniFi PoE budget planning mistakes happen before a single cable is pulled — at the switch selection stage.

9. Common PoE Planning Mistakes

• Connecting PoE+ devices to 802.3af-only switches: A PoE-only switch will refuse to power a PoE+ device, or worse, attempt to power it at reduced voltage causing instability
• Using total port count as capacity planning: A 48-port switch with 185 W total budget is not a 48-camera switch — it’s a 46-camera G5 Bullet switch or a 9-camera AI Pro switch
• Ignoring startup surge: During a power cycle event, all cameras attempt to draw maximum power simultaneously — budget for this scenario in addition to steady-state consumption
• Mixing PoE standards on the same switch without checking per-port capability: Some switches provide PoE++ on only a subset of ports — verify per-port capabilities before connecting high-power devices
• No UPS on IDF switches: A power outage that drops all cameras simultaneously prevents incident documentation precisely when footage matters most — protect IDF switches with UPS

Use this UniFi PoE budget planning checklist on every commercial deployment before hardware is ordered.

10. PoE Planning Checklist

UniFi PoE Budget Planning Services by 2M Technology

• VLAN design for commercial security systems
• UNVR Pro storage sizing guide
• G5 Bullet commercial deployment guide
• UniFi commercial deployments in DFW
• Back to UniFi Deployment Center

Frequently Asked Questions