PoE Power Budget for Factory Cameras in India: Sizing It Right
Power-over-Ethernet (PoE) carries both data and power to a camera over one Cat5e/Cat6 cable, so you size the switch by adding up every camera's wattage and keeping under two limits at once: the per-port cap and the switch's total power budget — then leave 20-30% headroom. In India the harder half of the job is keeping that switch and the NVR alive during load-shedding, which means putting them on a UPS (and ideally the DG set), because a camera that goes dark during a power cut is worse than no camera at all.
Most mid-size Indian factories get the camera count right and then get the power wrong — a switch that trips when the IR illuminators kick in at night, or a whole camera bank that dies the moment the grid drops and the plant runs on generator. This guide walks the PoE watt math plainly, then covers the India-critical part: designing so the cameras stay watching through a power cut.
What PoE actually is
PoE sends DC power and Ethernet data down the same twisted-pair cable. One run from a PoE switch (or an NVR with built-in PoE ports) to the camera — no separate 12V adaptor, no electrician pulling mains to a roof truss. That is why it dominates factory CCTV: fewer cables, one point to protect during a power cut, and centralised control.
The practical cable limit is about 100 m per run over Cat5e/Cat6 for both data and power. Past that you need a PoE extender, a fibre media converter, or a local switch — relevant in long sheds and yard runs where the gate camera sits far from the server room.
IEEE classes and how many watts each gives
PoE is standardised by IEEE 802.3. The key point: the switch sources more watts than the camera receives, because some is lost in the cable. Plan against delivered watts at the camera.
| Standard | Common name | Power at source (indicative) | Delivered at device (indicative) | Typical use |
|---|---|---|---|---|
| 802.3af | PoE | ~15.4 W | ~12.95 W | Fixed dome/bullet, no heater |
| 802.3at | PoE+ | ~30 W | ~25.5 W | IR bullets, small PTZ, mild heaters |
| 802.3bt (Type 3/4) | PoE++ | up to ~60-90 W | lower after cable loss | Large PTZ, heaters, multi-sensor |
Figures are the IEEE-defined maxima and are indicative for planning; the standard itself is the primary reference (IEEE 802.3). Note the naming trap: "PoE+" and "PoE++" are marketing shorthands for the 802.3at and 802.3bt standards — buy to the IEEE number, not the marketing badge.
What a factory camera actually draws
Vendor datasheets vary, so treat these as indicative and always confirm against the specific model's spec sheet:
- Fixed dome / bullet, IR on: roughly 4-12 W. Fine on 802.3af for many models, but IR-heavy night draw pushes some to PoE+.
- PTZ (pan-tilt-zoom): substantially more — the motors and longer-range IR often need 802.3at or 802.3bt.
- IR illuminators and housing heaters: these are the surprise. A camera that idles at 5 W in daytime can spike well past that when IR floods on at dusk or a heater cycles. Size for the peak, not the datasheet idle figure.
The lesson: budget every camera at its worst-case draw, not its typical one, or the switch will hit its cap exactly when you need night vision most.
Computing the total switch budget
Two caps must both hold:
- Per-port cap — no single port may exceed the class it supports (e.g. a 30 W PoE+ port cannot feed a 60 W PTZ).
- Total switch power budget — every switch has a total PoE budget (its "PoE power budget", a number on the spec sheet), often less than the sum of all ports at maximum. An 8-port switch where each port can do 30 W does not necessarily deliver 240 W total.
The formula:
Sum of each camera's peak draw + 20-30% headroom ≤ switch total PoE budget, and every camera's peak ≤ its port's class cap.
Headroom covers cable loss, simultaneous IR spikes, and future cameras. Undersize and the switch silently drops power to the lowest-priority ports — losing cameras with no obvious alarm.
Worked example: 8-camera shed
| Camera | Role | Class | Peak draw (indicative) |
|---|---|---|---|
| 1-4 | Fixed bullets, aisles, IR | 802.3af | 10 W each = 40 W |
| 5-6 | Fixed domes, work cells | 802.3af | 8 W each = 16 W |
| 7 | Gate PTZ, long-range IR | 802.3at | 25 W |
| 8 | Dispatch dock bullet, IR | 802.3af | 11 W |
| Subtotal | 92 W | ||
| +25% headroom | ~115 W |
A switch with a total PoE budget of ~120 W or more (and at least one PoE+ port for the PTZ) covers this comfortably. Buy the next size up if you expect to add cameras — see how many cameras a factory floor needs before you fix the count.
The India part: cameras must survive load-shedding
In most Indian industrial areas, scheduled power cuts and load-shedding are routine, and plants ride through on a DG (diesel generator) set with a UPS bridging the changeover gap. Your CCTV has to live inside that reality. A camera bank that goes dark every time the grid drops is not a security system — it is a system that fails precisely during the highest-risk windows (shift changeover in the dark, an unattended plant on generator).
Design rules that matter more than any watt calculation:
- Put the PoE switch AND the NVR on a UPS. Both must ride the seconds-to-minutes gap between grid loss and the DG picking up load. If only the NVR is on UPS but the switch is not, every camera still goes dark — the switch powers them.
- Feed that UPS from a DG-backed circuit. A UPS alone rides a short cut; for hours-long load-shedding the UPS must itself be fed from a generator-backed line, or its battery drains and the cameras die anyway.
- Size the UPS for the switch's real PoE draw, not just its idle rating. A switch pushing 115 W of PoE plus its own electronics is a real load on the UPS runtime maths.
- Protect the whole chain: camera → switch → NVR → viewing/uplink. A single unprotected link (an unbacked network switch feeding the uplink, say) breaks the record during exactly the cut you cared about.
This is not optional polish. A service like Mama, which watches the floor through the cameras and messages you what is running, idle or unsafe, can only do its job while the cameras are powered and streaming. Every minute the switch is dark is a blind minute — and load-shedding blindness tends to land at night, when idle machines and safety risks are hardest to catch by walking the floor. For context on what continuous coverage is worth: a single 24/7 manned guard post in India runs an indicative ₹75,000-1,40,000/month fully loaded, and it still cannot watch every zone at once.
Where this sits in the bigger decision
PoE budgeting is one line item in the system. Storage (NVR vs cloud) has its own power and continuity implications — covered in NVR vs cloud video storage in India — and the full build cost, including switches and UPS, is broken down in what a factory camera AI system costs in India.
Two honest limits worth stating: wattage figures above are indicative — always size against the exact camera and switch spec sheets, since IR and heater peaks vary widely by model — and PoE budgeting cannot fix an undersized generator or a UPS with dead batteries. Get the power-continuity chain right first; the watt arithmetic is the easy half.
Quick checklist
- Confirm each camera's peak draw (IR/heater on), not idle.
- Match every port to the right IEEE class (af / at / bt).
- Keep total load ≤ switch PoE budget, with 20-30% headroom.
- Keep runs under ~100 m; extend with fibre or a local switch beyond that.
- Switch + NVR on UPS, UPS fed from a DG-backed circuit.
- Test it: cut the grid and confirm every camera stays up.
Further reading on standards: the IEEE 802.3 Ethernet standard is the authoritative source for PoE power classes.