PoE budget
Switch budget vs device load — does your PoE switch carry the install?
List the PoE devices on a switch, enter draw and count, and see the budget allocated by class (what a switch reserves without LLDP) or by actual draw. Devices are checked against 802.3af/at/bt power-at-device limits, headroom is reported as a percentage of budget, and you're told when to step up a class, split across switches, or add a midspan injector.
Default and the safe assumption: without LLDP-MED / CDP power negotiation, the switch reserves the full class wattage (15.4 / 30 / 60 / 90 W) for every device the moment it links, regardless of what it really draws. A 7 W phone still costs 15.4 W of budget.
- ▸ Cable loss over 100 m of Cat5e/6 (the gap between port and device values): 802.3af ~2.5 W · 802.3at ~4.5 W · 802.3bt Type 3 ~9 W · Type 4 ~19 W. Shorter runs deliver more; the standard does not let you count on it.
- ▸ Two-pair (af/at) vs four-pair (bt): bt devices on an at switch fall back to at power if they support it, or fail classification if they do not.
- ▸ A midspan injector powers a single drop from its own supply, so a 60 W or 90 W device can sit on an af/at switch without touching its budget.
- ▸ Bundled PoE cables warm up — NEC 725.144 / TIA TSB-184-A derate ampacity for large bundles of bt cables.
Each run feeds one device row. The bar shows budget allocated by class against the switch total.