LV Handbook › Tools › Network & Cabling › PoE Switch Power Budget

PoE Switch Power Budget

Add every PoE device by class and check the total against the switch budget and port count.

Switch

Total PoE budget from the switch datasheet
Class allocation reserves each port at its class maximum. Use actual draw only if the switch datasheet says it budgets by consumption.

Devices

Budget

Allocated
—
Left over
—
Ports used
—
DeviceQtyAt switchAt device
At the switch (PSE) and at the device (PD), per IEEE 802.3af / 802.3at / 802.3bt class tables. Class allocation budgets each port at its class maximum; device draw budgets at the wattage you enter.
Allocated / budget
—

Questions

How much power does each PoE class get?

At the switch: Class 1 4 W, Class 2 7 W, Class 0 and 3 15.4 W (802.3af), Class 4 30 W (802.3at), Class 5 45 W, 6 60 W, 7 75 W and 8 90 W (802.3bt). The device side gets less because of cable loss: 3.84, 6.49, 12.95, 25.5, 40, 51, 62 and 71.3 W.

Should I budget by class or by actual draw?

Use class allocation if the switch reserves each port at its class maximum. Use device draw only if the switch datasheet says it allocates by actual consumption.

How much headroom should I leave?

Keep part of the budget free for cold-weather heaters on outdoor cameras, IR at night and devices added later. The headroom line on the bar shows where that starts.

Is this the same as the PoE distance calculator?

No. The PoE Distance Budget checks one cable run. This adds up every device on one switch.

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