What is a PoE power budget?
It is the total wattage a switch can deliver across its PoE ports, which can be lower than the switch’s overall electrical input rating.
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PoE Calculator
Cameras that reboot at night are almost always an underpowered switch. Enter your cameras, watts and switch budget — see pass or fail before you buy, with IR headroom built in.
Check your power budget
PoE standards reference
| Standard | Per port | Powers |
|---|---|---|
| 802.3af (PoE) | 15.4 W | Fixed cameras, phones, APs |
| 802.3at (PoE+) | 30 W | IR bullets, small PTZ, multi-sensor |
| 802.3bt (PoE++) | 60–90 W | Big PTZ, heaters, LED, NVRs |
Two budgets matter: per-port wattage (the standard) and the total switch budget — a "PoE+" 8-port switch with a 65W budget can't run 8 × 12W cameras. Long runs (250 ft+) lose 10–15% as heat, so keep headroom.
Field wisdom
The night-reboot trap
Dusk hits all at once
Every camera's IR kicks on within minutes of each other — total draw jumps 30–50% simultaneously.
Brown-out, reboot, repeat
Past the budget, ports sag and cameras cycle — dropping footage exactly when incidents happen.
The 20% rule
Size the switch at max camera draw + 20%. Growing later? Leave a third of the ports and watts free.
Answers
PoE questions
How many watts does a camera use?
Fixed IP cameras: 4–8W (+2–4W when IR turns on). PTZ: 15–30W+. Heated or active-deterrence models: 20–40W. Size from the max rating, not idle.
802.3af vs at vs bt?
af = 15.4W/port, at (PoE+) = 30W, bt (PoE++) = 60–90W. Fixed cameras run on af/at; PTZs and heaters usually need at/bt.
Why do cameras reboot at night?
IR turns on at dusk, total draw jumps past the switch budget, ports brown-out and cameras cycle. Keep 20% headroom above max draw.
Does cable length matter?
Yes — 10–15% power is lost on long runs (up to the 328 ft limit). Use real copper (not CCA) and keep budget headroom.
Want the switch sized before you buy?
Hi-Tech specs the switch, cabling and camera power for Cleveland, Akron and Canton installs — free review, no obligation.
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