Power over Ethernet (PoE) lets a single network cable carry both data and electrical power to a device, which is why nearly every modern IP camera, door reader controller, intercom, and access point can run without a separate power supply at the endpoint. The three tiers you will hear about — PoE, PoE+ and PoE++ — are formal IEEE standards that differ mainly in how many watts the switch can deliver to each port. Pick the wrong tier and your cameras will reboot in cold weather, your readers will brown out when locks fire, and your "finished" install will generate service calls for months. This guide explains what each tier actually delivers, where the power goes, and how to spec it correctly the first time.
The three tiers at a glance
All three standards run over ordinary twisted-pair Ethernet cabling and are backward compatible — a PoE++ switch will happily power a basic PoE camera, just not the other way around. The difference is the power budget per port, defined by the IEEE 802.3 family:
- PoE (IEEE 802.3af) delivers up to roughly 15.4 W at the switch port, with about 12.95 W usable at the device after cable loss. Enough for a fixed-lens indoor camera, a simple intercom, or a basic reader.
- PoE+ (IEEE 802.3at) delivers up to roughly 30 W at the port, with about 25.5 W at the device. This is the practical workhorse tier for outdoor cameras with heaters, motorized varifocal lenses, and modest pan-tilt-zoom (PTZ) movement.
- PoE++ (IEEE 802.3bt) comes in two types: Type 3 delivers up to roughly 60 W at the port (about 51 W usable) and Type 4 up to roughly 100 W at the port (about 71 W usable). This tier powers high-end PTZ domes, multi-sensor panoramic cameras, illuminators, and edge devices that drive locks or auxiliary loads.
A useful mental model: every step up the ladder roughly doubles the available power. The numbers above are nominal — always design to the device's worst-case draw, not its idle draw.
Where the watts actually go
The headline question — "how many watts does my camera need?" — hides the real engineering. Power gets consumed in three places, and security devices are unusual because their peak load is intermittent and weather-driven.
The device's steady-state electronics. A fixed indoor camera might draw 4–7 W continuously for the sensor, encoder, and network chip. That is comfortably inside plain PoE.
Optional subsystems that spike. This is where budgets blow up. An integrated IR or white-light illuminator can add 5–15 W when it switches on at dusk. A built-in heater and blower on an outdoor housing can pull 10–20 W when temperatures drop below freezing — and it engages exactly when you are least able to send a technician. A PTZ motor draws a burst every time the camera slews to a preset. None of these run during a daytime bench test, which is precisely why undersized installs pass commissioning and fail in January.
Cable loss. Copper has resistance, so some power is dissipated as heat over the run. That is why the standards quote two numbers — watts at the port versus watts at the device. Longer runs and thinner conductors lose more. The 100-meter channel limit that governs Ethernet data also bounds your power delivery; push past it and both data and power degrade.
Readers, controllers, and the access-control wrinkle
Cameras dominate the PoE conversation, but access control is where buyers most often get burned. A credential reader by itself sips power. The trap is what the reader's controller is being asked to drive: electric strikes, magnetic locks (maglocks), request-to-exit sensors, and door position switches.
A maglock holding a heavy door can draw 500 mA or more continuously, and an electric strike pulls a sharp inrush current at the moment it actuates. When integrators try to power a door's full hardware stack from a single PoE port through a PoE-to-lock controller, PoE++ Type 3 or Type 4 is usually the honest requirement — and even then you must budget every connected load, not just the reader. Underpowering a door does not announce itself politely; it shows up as a lock that intermittently fails to release, which is both a security failure and a life-safety concern on egress. When in doubt, separate the lock power from the data path or move up a tier with margin to spare.
How to spec it without guesswork
Treat power as a design deliverable, not an afterthought. A repeatable approach:
- List every endpoint and its worst-case draw. Read the manufacturer's maximum power rating, including heater and illuminator, not the typical figure. Add a margin of at least 20–25 percent on top.
- Sum the loads against the switch's total power budget. A 24-port switch advertised as "PoE+" rarely means 30 W on all 24 ports simultaneously. Check the aggregate power supply budget in watts and confirm it covers your fully loaded, worst-case total — not the average.
- Account for cable length and gauge. Long runs lose power; if you are near the 100-meter limit with marginal devices, step up a tier or shorten the run with an intermediate switch or media converter.
- Plan for redundancy. Cameras and doors are security infrastructure. Decide up front whether PoE switches sit behind a UPS, and for how long they must ride through an outage. PoE concentrates many devices behind one switch, which is convenient until that switch loses power.
- Document the as-built power map. The watt budget you designed should live in the closeout package so the next technician does not unknowingly overload a port by adding "just one more camera."
Where compliance fits the power conversation
For federal, defense, and many enterprise buyers, the switch delivering PoE is not a neutral commodity — it is networking gear subject to NDAA Section 889 and TAA requirements. Section 889 prohibits certain covered telecommunications and video-surveillance equipment from named manufacturers in federal contracts, and that prohibition reaches the infrastructure layer, including switches and the cameras they power. A power-budget spreadsheet that ignores provenance can still produce a non-compliant bill of materials.
Because we are vendor-neutral, we are free to select the PoE switch, midspan injector, and endpoint that genuinely fit your power, environmental, and compliance envelope rather than steering you to one manufacturer's ecosystem. Our compliance-first, full-lifecycle approach means the power design, the equipment provenance, and the long-term maintenance plan are decided together — so the install that passes commissioning still passes an audit and still works two winters later.
The short version
Match the IEEE tier to the device's real worst-case load: plain PoE for simple indoor endpoints, PoE+ for outdoor cameras with heaters and lenses, and PoE++ for high-power PTZ, multi-sensor units, and PoE-driven door hardware. Then verify the switch's aggregate budget, respect the 100-meter channel, and plan for backup power. Getting PoE, PoE+ and PoE++ right is unglamorous, but it is the difference between a system that quietly works and one that generates a steady stream of cold-weather service tickets.
Want a power and infrastructure design that holds up to both winter and an audit? Talk to our integration team about your video and access project.