A switch’s PoE budget is the total amount of power it can deliver to powered devices. That total budget is separate from the maximum amount any one port can provide.
Use the free PoE Budget Calculator for a quick design check.
List every powered device
Include access points, cameras, phones, intercoms, access-control devices, sensors, PoE-powered downstream switches, and any other powered equipment.
Use conservative power values
For early design, use manufacturer maximum power draw or a documented design value rather than the lowest number you have ever observed in production.
Real-time power consumption can be lower than maximum, but design headroom helps accommodate boot events, infrared illumination, radios under load, USB accessories, and future changes.
Total device load
Add the design wattage of every device. Then compare that total with the switch’s available PoE budget.
Do not forget per-port standards
A switch can have enough total PoE budget but still fail to power a specific device if the individual port does not support the required PoE standard or power level.
Example
| Device | Quantity | Planning watts each | Total |
|---|---|---|---|
| Access points | 8 | 18 W | 144 W |
| Cameras | 12 | 10 W | 120 W |
| Phones | 6 | 5 W | 30 W |
| Total | 294 W |
A 300 W switch would technically look close, but it provides almost no design headroom. A higher budget may be more appropriate depending on the devices and expansion plan.
Plan for growth
If the rack has unused ports likely to be populated later, reserve power for expected growth. Otherwise the customer may discover that adding two cameras requires replacing a switch.
UPS sizing
PoE load also affects UPS runtime. A switch drawing 350 W because it powers cameras and APs behaves very differently during an outage than an empty switch drawing 40 W.
Frequently asked questions
Is total PoE budget the same as switch power consumption?
No. PoE budget describes power available to powered devices. The switch itself also consumes power.
Can I rely on current observed PoE usage?
Observed usage is helpful for existing environments, but design values should account for peak or maximum conditions.
Should every PoE switch have unused budget?
Some headroom is usually desirable. The amount depends on device behavior, expected growth, redundancy, and business requirements.