PoE Budget Calculator.
— PoE budget · IEEE 802.3 af / at / bt
Count what the switch must power today.
Aggregates per-device wattage per IEEE 802.3bt Type 1–4 class tables and adds 30% spare headroom for a five-year refresh. A planning figure, not a procurement spec.
Recommended budget
125 W
96 W expected draw + 30% headroom
Switch tier
Tier 1
24-port switch, 16 PoE+ ports · 190 W published pool · one chassis
Devices counted
8
your counts · 16 802.3at (PoE+) ports per chassis
Largest single device
18 W
IEEE 802.3at (PoE+) — sets the per-port floor
A planning link that reopens this exact configuration — not a quote.
The power pool is shared across ports — it is not a per-port allowance.
- sku class
- NETGEAR GS324P — 190 W shared across 16 of its 24 ports — engineering reference, not a quote
- powered ports
- 16 of 24 ports power 802.3at (PoE+) on one chassis · 8 devices counted · one chassis
- shared pool
- Budget is a shared pool across ports, not a per-port figure
- draw basis
- EXPECTED draw at the powered device — a planning figure for the family, not the datasheet maximum of any one model and not a measurement
- device counts
- USER INPUT — whatever you entered on the left
- switch pool
- MANUFACTURER MAX — 190 W published · Internal fixed supply; no PoE upgrade path
- port ceiling
- MANUFACTURER MAX — 25.5 W to the device on one port at this tier (IEEE PD ceiling)
- port count
- MANUFACTURER MAX — 16 of the 24 ports can power 802.3at (PoE+). Ports and watts are independent: this is what one chassis can terminate, whatever the pool
- class source
- IEEE 802.3 af / at / bt class tables
- channel loss
- Not modelled — the spare below has to cover it
- cabling
- TIA/EIA-568-C · ISO/IEC 11801 Cat6A
- headroom
- 30% — fixed, and not adjustable in this tool
+ Model assumptions (9)− Model assumptions
Indicative — class wattages per IEEE 802.3 af / at / bt tables; a switch PoE budget is a shared pool across ports, not a per-port figure. The wattages counted here are what each device draws at the powered end; a switch pool is quoted at the sourcing end, and the gap between them — plus cable loss over a long run — is not modelled and has to come out of the spare shown above. Tier budgets assume the power supplies named beside them; several of those chassis reach the stated pool only when both supply bays are populated. Production designs ship with a per-port budget allocation spreadsheet.
What changes this estimate
- Exact device models and their datasheet PoE class
- Cable-run lengths near the 100 m limit (PSE-to-PD derating)
- Device growth across the five-year refresh
- Which physical ports the rack schedule allocates — the count is modelled, the plan is not
A planning link that reopens this exact configuration — not a quote.
Those figures travel with you, labelled as carried and editable there. The 96 W carried is the expected device draw, before this tool’s 30% headroom — the network calculator’s own PoE figure carries none, so the two arrive on the same footing.
The Engineering Project Workspace opens with 4 cameras, 8 powered devices and 96 W of PoE load ready to add. Nothing is added until you choose to. This workspace is kept in this browser only. Nothing is uploaded, nothing reaches TechnoGuru, and clearing your site data clears it.
IT · Networking · IEEE 802.3
Count the PoE-powered devices on the network — phones, cameras, APs, intercoms, sensors, AV nodes — and the tool sizes the switch PoE budget, the IEEE 802.3 class each device needs, and the SKU class. 30% headroom is built in and fixed; there is no headroom control, because a five-year refresh is the assumption the whole figure rests on.
- PoE classes
- af · at · bt
- Headroom
- 30% fixed
- Switch tiers
- 6
- SKU class
- Aruba · Cisco · NETGEAR
Field notes · why the model is shaped this way
PoE budget is a shared pool
A 48-port PoE+ switch with 740 W cannot drive 30 W per port simultaneously — only about 24 of the 48 ports can run at the full 30 W at once.
High-draw devices need 802.3bt
Wi-Fi 7 APs draw about 32 W — above the 25.5 W a PoE+ port can deliver to the device — so specify 802.3bt Type 3 ports. Heated PTZ cameras at 55 W go past Type 3's 51 W device ceiling and need Type 4.
30% headroom is the rule
Five-year refresh cycles see device counts grow about 6% a year. 30% spare keeps the switch in budget across the cycle. It is applied unconditionally — the tool has no override, and a genuinely static device count is a conversation for the design review rather than a slider.
Ports are a second, independent limit
Watts and ports are sized separately and the answer is whichever is larger. A 24-port chassis terminates 24 powered devices however small their draw, so an estate of 25 low-wattage sensors needs a bigger switch even though the pool was never in question. The calculator above floors on port count as well as wattage and IEEE class, and says how many chassis the estate takes.
Operationally sensible ecosystem
Brands grouped by engineering role — not random logos.
Network backbone
Core switching + routing + firewall
- HPE Aruba 6100L2 managed PoE+ for mid-market
- Cisco Catalyst 1300L2 managed PoE+ alternative
- FortiGateMid-market UTM firewall
Wi-Fi access
High-density Wi-Fi 6E / Wi-Fi 7
- HPE Aruba 530Wi-Fi 6E for enterprises
- Cisco Catalyst 9120Wi-Fi 6E with controller
IP cameras
Cameras + analytics edge
- Hanwha WisenetKorean enterprise vendor
- Bosch IPEuropean optics + analytics
- Hikvision ProMid-tier Hikvision product line
· Starting configurations
Typology presets — pick a scenario, see the calculator.
Each preset opens a curated configuration page with the engineering reasoning behind the numbers. Then the calculator loads with the same inputs — change them and the URL stays shareable.
· Engineering advisory · PoE Budget Calculator
What the wattage budget predicts about the network.
The recommended switch tier is the brief-stage budget. The deployment requires the cable-length derating, the day-two refresh discipline and the operational consequence below.
Deployment observations
- Switch advertised PoE budget is the shared pool across all ports, not the per-port allocation. A 48-port PoE+ switch with a 740 W budget cannot deliver 30 W on every port simultaneously — at full load, ports beyond the budget power-cycle rather than negotiate down.
- Port count is a constraint of its own and it binds first on low-draw estates. Sensors, readers, fixed cameras and handsets draw so little that the pool is never the limit — the number of powered ports is, and on an 802.3bt chassis the count that matters is the count at the class the estate needs, which is lower than the chassis port count. The switch quantity is the larger of the power-derived and the port-derived number, never the power one alone.
- Type 3 (60 W cable / 51 W device) is the floor for Wi-Fi 7 APs, large 1080p PTZ cameras with heaters and most AV-over-IP encoders; Type 4 (90 W / 71.3 W) is reserved for video-bar systems and large heated outdoor cameras. Most enterprise networks today are predominantly Type 3, and the Type 4 budget is reserved at the rack head-end.
- Cable-length losses are real beyond 60 m runs — Cat6A holds 100 m at full PoE++ budget, Cat6 derates ~5% near the limit. The 30% spare absorbs both the device growth and the cable-length derating.
Redundancy posture
- PoE switch failure pulls every powered device offline — cameras, APs, phones, intercoms all dark simultaneously. Stacked-switch architecture (Cisco IOS-XE / Aruba VSF) shares the PoE budget across the stack and tolerates a single-switch event without losing every device on that switch.
- Switch PSU redundancy (dual-PSU class) holds the PoE budget through a single PSU failure; without it, a PSU event drops half the PoE budget on a single-PSU class switch and triggers cascade port-shutdown.
Environmental considerations
- Switch thermal load grows with the active PoE budget — a fully-loaded PoE++ switch dissipates 200-400 W of heat at the rack, which is the dominant rack-AC load on a typical IT cabinet. Rack ventilation is sized against the active PoE budget, not the data-only load.
- Outdoor PTZ cameras with heaters can draw 30 W in winter and 14 W in summer — the budget must hold the winter peak, not the summer baseline. Per-camera draw varies with ambient temperature and operating mode.
Commissioning discipline
- Link-budget test on every PoE run at handover — per-port PoE class negotiation, per-port wattage delivery verification under the actual device load, signed off in the as-built rack-and-port schedule.
- Per-port PoE class assignment documented at handover — not every port runs every device class; assignment to the right port matters for budget planning and for cable-length derating discipline.
- Configuration baseline export for the switch stack — port descriptions, VLAN assignment, PoE class assignment and stack member identity stored offline for clean-slate recovery within the same business day.
Lifecycle implications
- Switch chassis carries an 8-10 year service envelope under enterprise duty; the PoE budget envelope grows generationally — Wi-Fi 6 to Wi-Fi 7 typically grows per-AP draw by 30-50%, which is what the 30% spare absorbs across a typical 5-year refresh.
- Per-port PoE chip wear is not a documented service-life signal but is the leading silent failure mode on heavily-loaded ports — replacement is a like-for-like switch swap, not a chip-level repair.
Expansion readiness
- Port count expansion typically lives in the existing stack capacity until the stack is full; beyond that, a new stack member or a parallel stack is the minimum incremental scope.
- Generational PoE-class upgrade (PoE+ → PoE++ Type 3) is a switch refresh — the cable plant carries the higher class without re-cabling, but the switch chassis must support the new class.
Verification status: Conditional engineering model — assumptions stated · Adversarially verified and regression-guarded · reviewed 2026-08-30
· Engineering notes
How to read this tool’s output
Stage 3 (design) or stage 4 (BOQ). Use during switch-sizing to validate the PoE class and SKU.
The assumptions, limits and reference architectures behind this
What an engineer should know
The assumptions behind the numbers this tool produces.
- PoE-powered device counts in — total watts, switch tier (PoE+ / PoE++ Type 3 / Type 4) and indicative SKU band out.
- 30% headroom is built in and is not adjustable in the tool — it is sized for a five-year refresh. A genuinely static device count needs less than that, which is a judgement for the design review rather than a slider.
When this tool is the right one
The project moments and room types this is built for.
- IT lead sizing the switch class for a Wi-Fi 7 + IP surveillance refresh.
What changes the answer in practice
Field conditions that move the result away from the planning figure.
- Type 4 (90 W) PoE++ powers small displays and high-end APs, but cable plant must be Cat6A end-to-end.
Defensible starting architectures
Vendor-neutral reference points, not a recommendation to buy — the right answer is the one that survives your site survey.
- PoE++ Type 3 backbone for standard deployments; Type 4 reserved for devices that need the headroom.
Common mistakes
Failure patterns we see on real projects.
- Treating PoE class as flat across device families — IR-illuminated cameras spike the actual draw.
How this lands against adjacent systems
What else has to be agreed before this output is safe to build to.
- Pairs with the Network Calculator for the year-three switch and AP count.
Where this tool fits
The building types this output is calibrated for — and, where we have said so, the ones it is not.
Best suited for
Not the tool to reach for
The standards and technologies this touches
Reference pages for the protocols, standards and systems behind this tool’s output.
· Why budget right matters
A 48-port switch advertised as PoE+ does not deliver 30 W on every port. The budget is a shared pool: 740 W split across 48 Wi-Fi 6 APs at 18 W expected draw comes to 864 W — over the pool by 124 W, which means some APs power-cycle under load. The opposite failure is just as common: 60 occupancy sensors fit that pool several times over and still do not fit the 48 powered ports. Every figure in those sentences is read out of this tool's own device table and switch ladder. Sizing against the actual device draw and the port count at design time, with 30% spare, is the difference between a network that runs and one that visits the rack at 3 a.m.
· Frequently asked
PoE Budget —
what people ask first.
What is a PoE budget?
A switch's PoE budget is the total watts it can deliver to powered devices across all ports combined. A 24-port PoE+ switch with a 370 W budget cannot supply 30 W on every port simultaneously — only about 12 ports can be fully loaded. The pool is not the only limit: that same chassis terminates 24 powered devices whatever they draw. Sizing against actual device draw plus headroom, and against the powered-port count, is the correct planning method.
Does the number of ports matter as well as the wattage?
Yes, and on low-draw estates it is the binding constraint. Power and ports are independent: a 24-port chassis with a 370 W pool has the wattage for dozens of 4-6 W sensors and the ports for 24 of them. On an 802.3bt chassis there is a third number — the ports capable of the class the estate needs, which is smaller than the chassis port count, because the heavier classes are offered on a subset of the ports. The right switch quantity is the larger of the power-derived and the port-derived figure. The calculator above floors on all three and states how many chassis the estate takes.
When do I need PoE++ Type 3 vs Type 4?
Type 3 (60 W cable / 51 W device) is needed for Wi-Fi 7 APs, large 1080p PTZ cameras with heater, small kiosk displays and some AV-over-IP encoders. Type 4 (90 W / 71.3 W) is reserved for video-bar systems, large pan-tilt-zoom-heated outdoor cameras, and powered displays up to 12 inches. Most enterprise networks today are predominantly Type 3.
Why 30% headroom?
Five-year refresh cycles see device counts grow ~6% per year and per-device draw increase as Wi-Fi standards advance. A 30% spare keeps the switch in budget over the cycle without forcing an early replacement. Beyond 30%, the cost premium of an over-sized switch tier is rarely justified. The figure is fixed in the tool — there is no control to change it, and the page no longer suggests otherwise.
Does the tool account for cable-length losses?
It uses the device-side wattage (after PSE-to-PD efficiency losses). For runs near the 100 m limit, derate the device draw by ~5% as a conservative buffer. Most premium installs land at 30–60 m runs where loss is negligible.
Will TechnoGuru spec the switch and install it?
Yes. Enterprise switching, structured cabling and PoE network design are core services. We specify Cisco, HPE Aruba and Juniper enterprise classes, with NETGEAR M-class as a value-tier alternative for SMB. End-to-end commissioning with link-budget testing on every PoE run.
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