A PoE switch can run out of two different things: power and the right kind of port. Budgeting PoE means checking both before the equipment is bought. This note uses numbers from Ubiquiti’s own documentation, and it points out where the arithmetic is only an illustration.
We work primarily in UniFi, and we also service other systems. PoE budgeting works the same way on any switch, but the numbers below are for UniFi.
Two limits, not one
Total power. Ubiquiti calls this PoE Availability: the total watts a switch can share among all connected devices. Ubiquiti’s rule is that PoE Availability must be greater than the sum of all device power requirements, or you risk instability or failure. The total is shared, so a switch with many PoE ports cannot power every port at full draw. Ubiquiti lists the range by switch class:
| Switch class | PoE Availability |
|---|---|
| Lite | 45 to 52 W |
| Standard | 42 to 195 W |
| Professional | 120 to 600 W |
| Pro Max | 180 to 720 W |
| Enterprise | 120 to 720 W |
| Enterprise Campus | 950 to 1,050 W |
Port type. Each port supports a PoE standard, and each device needs a certain one. Ubiquiti’s table:
| Name | Standard | Max power per port | Max power to the device |
|---|---|---|---|
| PoE | 802.3af | 15.4 W | 12.95 W |
| PoE+ | 802.3at | 30 W | 25.5 W |
| PoE++ | 802.3bt | 60 W | 51 W |
| PoE+++ | 802.3bt | 100 W | 71 W |
The device gets less than the port supplies because some power is lost in the cable. A switch can have enough total watts and still have no port of the type a device needs.
What common devices draw
Ubiquiti publishes a power consumption figure for each device. A few that show up on our jobs:
| Device | Listed power |
|---|---|
| G5 Bullet camera | 5 W |
| AI Pro camera | 11 W |
| Intercom | 13 W |
| U7 Outdoor access point | 19 W |
| U7 Pro access point | 21 W |
| U7 Pro XGS access point | 29 W |
| Door Hub | 30 W |
Check each device’s tech spec for the PoE type it needs. For example, Ubiquiti lists the U7 Pro XGS power method as PoE++ with a 10 GbE uplink, and lists the Door Hub, Door Hub Mini and Gate Hub as PoE++ too.
Hubs that supply PoE to readers and cameras draw more than their base figure. Ubiquiti lists the Gate Hub at 22 W without PoE output and 60 W with it, so count the readers on a hub as part of that hub’s load.
A worked example (an illustration, not a customer job)
Say a plan has six AI Pro cameras, two U7 Pro XGS access points and one Intercom. Using Ubiquiti’s listed figures: 6 x 11 W is 66 W, 2 x 29 W is 58 W, and 13 W for the Intercom. The total is 137 W.
Now look at a real switch. Ubiquiti lists the Pro Max 16 PoE with 180 W total PoE and a port layout of twelve PoE+ ports (1 GbE) and four PoE++ ports (2.5 GbE). On power, 137 W fits in 180 W, with 43 W to spare. On ports, the two U7 Pro XGS units need PoE++, and this switch has four of those, so they fit too. One more detail: the PoE++ ports on this switch are 2.5 GbE, while the U7 Pro XGS has a 10 GbE port, so the link would run at no more than the switch port’s 2.5 GbE. That might be fine for the job, or it might push you to a switch with faster PoE++ ports. Either way, it is better to find out on paper.
How we budget a job
- List every powered device from the plan: cameras, access points, Access hubs, readers and the intercom.
- Look up each device’s listed power and the PoE type it needs.
- Add them up and compare with the switch’s total PoE. We keep headroom, because jobs grow. That headroom is our practice, not a Ubiquiti figure.
- Check that there are enough ports of the right type, and that the port speed suits each device.
- Label the ports so the map matches the rack.
If an old recorder was powering the cameras through its own ports, the new switch has to take over that whole load, both ports and watts.
PoE adapters
A PoE adapter can power a device when there is no PoE switch, or take devices off a switch that has run out of power. Ubiquiti notes its adapters are passive and always output voltage with no negotiation. That is fine for most PoE devices, but do not connect an adapter’s output to computers, printers or other non-PoE gear. We prefer fixing the budget to stacking adapters, because adapters add parts to track.
Cable
Ubiquiti lists Cat 5 or better for PoE+ and PoE++. Our cabling standard is CAT6 for cameras and CAT6A for data drops and Wi-Fi access points, labeled at both ends and tested. See CAT6 vs CAT6A for where each one fits.
FAQ
Does a switch with 16 PoE ports power 16 devices?
Only if the total power covers them. The total is shared across the ports, so power runs out before ports do on a camera or access point heavy switch.
Do I need PoE++ for Wi-Fi 7 access points?
It depends on the model. Ubiquiti lists the U7 Pro XGS as PoE++, and lists lighter draws for other U7 models. Check the tech spec for the exact one.
Can I just add a PoE adapter?
You can, within Ubiquiti’s cautions above. For a lasting install we plan the switch to carry the load.
Get a plan
Request an estimate. Bring a count of cameras, access points and doors and we will map ports and power to them. See our Wi-Fi installation page, or contact us.
