{{ result.summaryTitle }}
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{{ result.statusLabel }} {{ result.utilizationBadge }} {{ result.portBadge }} {{ result.modeBadge }}
Enter the total watts the switch can deliver to powered devices across all PoE ports.
W
Count only ports that can provide PoE in this switch, stack, or injector shelf.
ports
Keep this part of the switch budget unused before judging the plan healthy.
%
Use actual PD watts for datasheets; use switch-side watts when copying values from a switch dashboard.
Adds switch-side watts above device-side draw when the basis is actual PD watts.
%
Rows use device,count,watts,standard,priority,cable length m. Standards accept 802.3af, 802.3at, bt3, or bt4.
Keep one device type per row; quoted CSV names are supported.
Optional extra draw for a restart scenario; leave 0 when planning reserve already covers it.
%
Set a fixed spare target for known future devices or site policy.
W
Choose how many decimals to show in visible tables and exports.
Metric Value Readout Copy
{{ row.metric }} {{ row.value }} {{ row.readout }}
Device Count Standard Priority Switch W Each Total Switch W Ports Status Copy
{{ row.device }} {{ row.count }} {{ row.standard }} {{ row.priority }} {{ row.switchEach }} {{ row.totalSwitch }} {{ row.ports }} {{ row.status }}
Priority Ports Switch W Retained W Action Readout Copy
{{ row.priority }} {{ row.ports }} {{ row.switchW }} {{ row.retainedW }} {{ row.action }} {{ row.readout }}
Tags: Devops, Networking, Sysadmin
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Power over Ethernet budget planning compares the watts a switch can supply with the watts that cameras, wireless access points, phones, controllers, and other powered devices are expected to draw. The same plan also has to fit the number of PoE-capable ports. A switch can have enough aggregate power and still fail the port count, or it can have empty ports while the power budget is already spent.

The planning number should be the published PoE budget for the switch, stack, or injector shelf, not the AC power-supply rating. Power sourcing equipment (PSE) loses some power in the cable before it reaches each powered device (PD), and higher-power standards reserve different amounts at the PSE than a device may consume at the far end. That distinction matters when a datasheet lists PD draw, while a switch dashboard reports switch-side watts.

Real sites need room beyond the steady-state sum. Infrared cameras can draw more at night, access points can change power after firmware or radio settings change, and a power event can restart many devices at once. A reserve target gives the plan space for those changes, while a separate boot-surge check shows whether a simultaneous restart would exceed the planning target.

Power over Ethernet budget stack showing device draw, cable allowance, reserve, spare capacity, and a separate port count warning.

A passing budget is still a model. It does not prove that a switch will negotiate the requested class, that passive PoE is compatible, that all cables meet the needed category and length, or that vendor-specific power modes are enabled. It gives a repeatable planning check before hardware is moved, added, or ordered.

Technical Details:

PoE budgeting has two related power numbers. PSE-side power is what the switch reserves or supplies at the port. PD-side power is what the device receives after cable loss. IEEE classes define ceilings for standardized negotiation, while real device draw can sit well below a class ceiling during normal operation.

Class ceilings are useful when the only trustworthy planning value is the standard or assigned class. Actual PD draw is useful when a datasheet lists device consumption. Switch-side draw is useful when the values come from an installed switch. Mixing those bases without adjustment can double-count cable loss or understate the power the switch must reserve.

Formula Core:

The budget calculation converts each inventory row into switch-side watts, sums the rows, then subtracts reserve and spare targets from the switch budget.

Wswitch each = Wentered×(1+Lcable percent100) Wplanned = ∑(Ndevices×Wswitch each) Wusable = Wswitch budget-(Wswitch budget×Rreserve percent100) Wspare after targets = Wusable-Wfixed spare-Wplanned Wboot draw = Wplanned×(1+Ssurge percent100)

In Actual PD watts plus cable loss mode, the first equation applies the cable-loss allowance. In Switch-side watts already include loss mode, entered watts are used as switch-side watts. In Reserve IEEE standard ceiling mode, a known 802.3 standard reserves the PSE ceiling for that row.

Standard Common type PSE ceiling PD ceiling Pair use
802.3af Type 1 15.4 W 12.95 W 2-pair
802.3at Type 2 30 W 25.5 W 2-pair
802.3bt Type 3 PoE++ / UPOE-class planning 60 W 51 W 4-pair capable
802.3bt Type 4 4PPoE 90 W 71 W 4-pair

The status readout is based on both power and validation results. Errors block the budget state until required inventory values are numeric. A negative Spare after targets means the plan exceeds the reserve and fixed-spare policy. A tight result can still have positive spare watts when the remaining room is less than 10% of the usable planning budget or when the boot-surge check goes negative.

Cue Boundary Meaning
Needs input Inventory has no valid rows, or count/watts cannot be read as numbers. Fix the rows listed under Check the PoE inventory.
Over budget Spare after targets is below 0 W. Move devices, lower reserve targets, or choose a switch with more PoE budget.
Tight budget Remaining spare is under 10% of usable budget, or Boot surge check is negative. Review high-draw devices and restart assumptions before adding more load.
PoE port demand Device count exceeds PoE ports available. Power may fit, but the switch still needs more PoE-capable ports.
Device warnings Unknown standard, inferred standard, passive PoE, zero values, or watts above the selected standard ceiling. Check the row before trusting the class or compatibility assumption.

Everyday Use & Decision Guide:

Start with the switch or stack specification. Enter the published aggregate PoE budget in Switch PoE budget and count only ports that can supply PoE in PoE ports available. Keep the Planning reserve at a conservative value when the site includes cameras, access points, door hardware, or devices that may change power draw after configuration.

Choose Device watts basis before entering the inventory. Use Actual PD watts plus cable loss when rows come from device datasheets. Use Switch-side watts already include loss when rows come from a switch report. Use Reserve IEEE standard ceiling when the plan should reserve the class maximum instead of expected draw.

The device inventory accepts one device type per row as device,count,watts,standard,priority,cable length m. The standard and priority entries are optional, but they improve warnings and the shedding plan. Supported standard entries include 802.3af, 802.3at, bt3, bt4, and passive PoE labels that prompt a manual compatibility check.

  • Budget Ledger shows switch budget, planned switch-side draw, reserve, usable planning budget, spare after targets, port demand, modeled PD-side draw, and boot surge.
  • Device Load Ledger shows each device type, count, standard, priority, switch watts each, total switch watts, ports, and row status.
  • Priority Shedding Plan keeps critical and high-priority groups first, then shows which lower-priority load must move or shed when budget is short.
  • PoE Load Stack visualizes planned draw, reserve, fixed spare target, remaining spare, or shortfall against the switch budget.
  • JSON keeps the current inputs, totals, device rows, priority groups, warnings, and errors together for handoff.

A spare-watt headline does not mean the switch is ready. Check PoE port demand, row Status, and Boot surge check before treating the result as usable. A plan with 40 W spare can still need another switch if it is six PoE ports short.

Use the result for a first pass before adding endpoints, splitting a camera group across switches, or deciding whether a larger PoE model is needed. Before ordering hardware, compare the output with the switch datasheet, device datasheets, cable length limits, and any vendor-specific power negotiation requirements.

Step-by-Step Guide:

Work from switch capacity to device rows, then read the budget and warning outputs together.

  1. Enter Switch PoE budget in watts from the switch, stack, or injector shelf specification. The Switch PoE budget row in Budget Ledger should match that value.
  2. Enter PoE ports available. Watch PoE port demand after the device rows are entered because port shortage is checked separately from watts.
  3. Set Planning reserve. The Planning reserve and Usable planning budget rows should move together as the percent changes.
  4. Choose Device watts basis. If you choose Actual PD watts plus cable loss, set Cable loss allowance before trusting Planned switch-side draw.
  5. Enter Device inventory rows as CSV. If Check the PoE inventory reports that count or watts must be a number, fix that row before using any summary value.
  6. Use Sample for a format example, Normalize to rewrite parsed rows into consistent CSV, or Reset inventory when you want to start again.
  7. Open Advanced when the plan needs Boot surge allowance, Minimum spare watts, or a different Rounding display.
  8. Read the summary, then check Budget Ledger, Device Load Ledger, and Priority Shedding Plan. Use the chart and JSON views after the warnings match the risk you are willing to carry.

Interpreting Results:

Spare after targets is the main power result because it subtracts the percent reserve and the fixed spare target before comparing load with capacity. PoE port demand is equally important. Positive spare watts with negative port spare means the device list still does not fit the switch.

Planned switch-side draw should be read with the selected basis. In actual-PD mode, it includes the cable-loss allowance. In switch-side mode, it assumes the entered watts already include loss. In class-ceiling mode, known standards reserve the PSE ceiling, which can make a conservative plan look much larger than the expected device draw.

Result field Trust cue Follow-up
Spare after targets At or above 0 W means the plan fits the reserve policy. If it is close to zero, review the highest-draw rows before adding devices.
PoE port demand Port spare at or above 0 means the device count fits the PoE port count. If ports are short, split the inventory across switches or use a switch with more PoE ports.
Boot surge check Negative spare after surge means a restart scenario exceeds the target budget. Stagger restarts, reduce the group, or increase the budget before relying on the plan.
Device Load Ledger Rows marked OK have no parser or standard warning. Investigate inferred standards, passive PoE, zero entries, and ceiling warnings.

Do not treat a healthy status as proof of field compatibility. Confirm the switch can negotiate the required class, the cabling supports the needed power, and passive PoE devices match the injector or switch hardware. The calculated budget is a planning result, not a live electrical test.

Worked Examples:

Mixed office switch with enough watts but too few ports

A 740 W switch with 48 PoE ports, 15% planning reserve, actual PD watts, and 10% cable-loss allowance is loaded with 12 Wi-Fi APs at 18 W, 16 IR cameras at 9 W, 24 desk phones at 5 W, and 2 door controllers at 25 W. Planned switch-side draw is 583.0 W, Modeled PD-side draw is 530.0 W, and Spare after targets is 46.0 W. The summary is still tight because only 46.0 W remains from the usable planning budget, and PoE port demand is 54 ports, which is 6 ports short.

Class-ceiling camera shelf

A 240 W shelf with 16 PoE ports and 20% reserve is checked in Reserve IEEE standard ceiling mode for 10 cameras entered as 9 W, 802.3af, normal priority. Class-ceiling mode reserves 15.4 W at the PSE for each camera, so Planned switch-side draw is 154.0 W. Usable planning budget is 192.0 W, Spare after targets is 38.0 W, and PoE port demand leaves 6 ports spare. That is a healthier planning case than using the same switch for the 54-port mixed inventory.

Restart check that turns a passing plan into a tight plan

Twelve access points at 18 W on a 300 W switch with 12 PoE ports, 15% reserve, actual PD watts, and 10% cable-loss allowance produce Planned switch-side draw of 237.6 W and Spare after targets of 17.4 W. Adding a 20% Boot surge allowance raises Boot surge check to 285.1 W and leaves 30.1 W short after surge. The fix is not a CSV formatting change; the restart scenario needs staggered recovery, fewer devices, or more switch budget.

Inventory row that needs correction

If a row reads Lobby AP,twelve,18,802.3at,high,50, Check the PoE inventory reports that the row count must be a number. Replacing twelve with 12 lets the row appear in Device Load Ledger, where the status can then show OK or a standard warning tied to the entered watts.

FAQ:

Which watts basis should I choose?

Choose Actual PD watts plus cable loss for datasheet values at the device, Switch-side watts already include loss for switch-reported draw, and Reserve IEEE standard ceiling when planning should hold the standard PSE ceiling for each row.

Why can the result show spare watts and still warn about ports?

Watts and ports are checked separately. Spare after targets can be positive while PoE port demand is short if the device count exceeds PoE ports available.

What standards can the inventory understand?

The standard column accepts common forms of 802.3af, 802.3at, 802.3bt Type 3, 802.3bt Type 4, bt3, bt4, and passive PoE labels. Unknown standards are kept as row warnings.

Does a healthy budget prove the switch will power every device?

No. The result models watts, ports, reserve, and row warnings from the entered inventory. It does not test LLDP, CDP, passive PoE wiring, cable quality, switch firmware behavior, or actual negotiation at the port.

How do I fix a count or watts error?

Use numeric values in the second and third CSV columns. A row such as Camera,8,9,802.3af,normal,80 can be parsed, while words such as eight or blank watts trigger Check the PoE inventory.

Glossary:

PSE
Power sourcing equipment, usually the PoE switch, injector, or midspan that supplies power at the Ethernet port.
PD
Powered device, such as a camera, access point, phone, controller, or sensor receiving PoE.
Switch-side watts
Watts supplied or reserved by the PSE before cable loss reaches the powered device.
PD-side watts
Watts consumed at the device after power has traveled through the cable.
Planning reserve
A percent of the switch budget held back before judging spare capacity.
Class ceiling
The PSE-side standard maximum reserved for a recognized PoE class or type.
Boot surge
An optional restart scenario that adds temporary draw above the planned steady-state load.
Priority shedding
A plan that keeps higher-priority device groups first when the usable budget cannot cover every row.

References: