Security & CCTV
PoE Budget Calculator
Every PoE switch has two limits - per-port class and total budget - and installs fail on the total more often than the port.
Calculator
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How it works
Total load = devices x watts each. Port classes: 802.3af delivers up to 12.95 W, 802.3at (PoE+) 25.5 W, 802.3bt up to 71 W. Keep about 10% of the switch budget spare for cable losses and startup surges.
Frequently asked questions
Why does my 8-port PoE switch drop cameras?
The total budget. Eight PTZ cameras at 20 W is 160 W - many "8-port PoE" switches budget only 120 W across all ports, even though each port alone could deliver 30 W.
What PoE class does a PTZ camera need?
Most PTZs need 802.3at (up to 25.5 W); large or heated ones need 802.3bt. Fixed domes usually run happily on 802.3af.