PoE Power Budget for Security Cameras: How to Calculate It
Calculate security-camera PoE power budget correctly using maximum device draw, total switch watts, per-port standards and planning headroom.
A PoE switch has two power limits that buyers regularly confuse: how much one port can deliver and how many total watts the switch can supply across all powered ports. Both must work for the design.
The basic power-budget formula
Required PoE budget ≈ sum of maximum camera watts × (1 + planning headroom). If six cameras are rated at 8W and two PTZ cameras at 20W, the base load is 88W. With 20% headroom, the planning target becomes about 106W.
Use maximum rated draw, not average daytime draw
A camera that normally consumes 5W may draw more when infrared LEDs, white lights, heaters, speakers or motors activate. Planning around the manufacturer's maximum PoE requirement reduces the risk of cameras rebooting precisely at night or during bad weather.
Per-port capability
| PoE family | Common source-side ceiling | Typical security use |
|---|---|---|
| 802.3af / PoE | 15.4W | Many fixed cameras |
| 802.3at / PoE+ | 30W | Higher-draw IR cameras, mini PTZ |
| 802.3bt / PoE++ | 60W or higher by type | Large PTZ, heaters, multi-sensor devices |
The camera datasheet controls the final choice. Do not assign a class based only on camera shape or resolution.
Total switch budget
A switch can advertise PoE+ on eight ports and still have a total budget far below 8 × 30W. The per-port label describes what an individual port can negotiate; the total budget determines how many devices the switch can sustain simultaneously.
Why headroom matters
Headroom covers power spikes, cable losses, added devices and operating changes. Twenty percent is a useful planning margin for many small surveillance systems, but extreme environments or future expansion may justify more.
Use the PoE Switch Power Budget Calculator to check watts, ports and uplink traffic in one place.