Quick answer
With the default example, a 120 W PoE+ switch can comfortably support four 8 W IP cameras and one 18 W Wi-Fi access point. 66 W recommended for 5 PoE devices on 8 PoE ports. The switch has enough PoE budget with useful headroom after reserve.
How to use this PoE switch power budget calculator
Start with the switch's published PoE budget. This is the power available to PoE devices, not the switch's total AC power consumption. Then enter how many PoE ports are available and the per-port PoE standard.
Add each device group using maximum device power from the data sheet. For cameras, use the higher value that includes infrared, heater, zoom, or PTZ movement when those features apply. For Wi-Fi access points, use the maximum PoE requirement, not average idle power.
This calculator checks three different limits: total PoE budget, available PoE ports, and per-port power. If the network issue is Wi-Fi coverage rather than PoE power, use the Mesh Router Coverage Calculator or Wi-Fi Extender Placement Calculator.
PoE switch power budget formula
device load W = quantity x watts per deviceswitch-side load W = device load W x (1 + cable loss %)recommended PoE budget W = switch-side load W x (1 + reserve %)remaining budget W = switch PoE budget W - recommended PoE budget WThe total budget calculation is only one part of PoE planning. A switch can have enough total watts and still fail if there are too few PoE ports or if a high-power device needs PoE+ or PoE++ on a specific port.
Assumptions and methodology
The calculator treats device watts as maximum powered-device consumption, then adds a cable-loss allowance and a design reserve. The default reserve is 20%, which is intentionally conservative for small camera, access point, and office networks.
- PoE checks per-port power separately from total switch budget. This matters for PTZ cameras and high-power access points.
- A switch with 8 Ethernet ports may not have 8 PoE ports. Count only powered ports.
- Passive PoE, proprietary injectors, and non-standard voltage devices are not interchangeable with standard 802.3af/at/bt PoE.
- Manufacturer device power can be listed as typical, maximum, class allocation, or adapter rating. Use maximum consumption for planning when possible.
Example calculations
PoE switch budget example
Suppose a small home or office install has four 8 W IP cameras and one 18 W Wi-Fi access point. The device load is 50 W before cable-loss allowance.
With the default cable-loss allowance, the estimated switch-side load becomes 55 W. After adding a 20%reserve, the recommended PoE budget is 66 W.
A 120 W PoE+ switch therefore has enough headroom for this device mix. If you later add PTZ cameras, outdoor heaters, or more access points, recalculate the budget before assuming the same switch is still enough.
PoE switch power budget chart
These examples show why device mix matters. Four small cameras can be easy for a modest PoE switch, while high-power access points or PTZ cameras may need a higher per-port standard and a larger total budget.
| Setup | Devices | Switch load | Recommended | Switch | Result |
|---|---|---|---|---|---|
| 4 indoor IP cameras | 4 | 35.2 W | 42.2 W | 60 W / PoE+ | Enough budget |
| 8 IP cameras | 8 | 70.4 W | 84.5 W | 120 W / PoE+ | Enough budget |
| 4 cameras + 2 APs | 6 | 74.8 W | 89.8 W | 120 W / PoE+ | Enough budget |
| 4 PTZ cameras | 4 | 96.8 W | 116.2 W | 150 W / PoE+ | Enough budget |
| 4 high-power APs | 4 | 154 W | 184.8 W | 250 W / PoE++ Type 3 | Enough budget |
Common PoE planning mistakes
The most common mistake is checking only the total PoE budget. A switch may have enough total watts but still fail if a PTZ camera or high-power access point needs more power than one port can deliver.
The second mistake is using average device power. Cameras with infrared LEDs, heaters, or motors may draw much more power at night or during startup. Access points may also need a higher PoE class to enable full radio performance.
The third mistake is filling every port with no reserve. Leaving headroom makes the setup more tolerant of cable loss, device replacement, firmware changes, and future expansion.
Related calculators
Dual Monitor Size Calculator
Estimate desk width and workspace fit for dual monitor setups.
Battery Charging Time Calculator
Estimate charging time from battery capacity, charger power, and charging efficiency.
Dehumidifier Drain Hose Calculator
Check whether a dehumidifier drain hose can work by gravity or needs a pump based on outlet height, drain height, and hose length.
Wi-Fi Extender Placement Calculator
Estimate where to place a Wi-Fi extender between the router and a weak-signal area using distance, walls, band, and extender type.
Mesh Router Coverage Calculator
Estimate how many mesh Wi-Fi units or satellite nodes a home may need from area, floors, layout, router location, backhaul, and coverage goal.
Router Backup Power Runtime Calculator
Estimate how long a UPS, DC mini UPS, power bank, or power station can keep a router, modem, ONT, or mesh Wi-Fi online.
FAQ
How do I calculate PoE switch power budget?
Add the maximum watts for every powered device, include a small cable-loss allowance if the watts are listed at the device, then add a reserve margin. Also check that the switch has enough PoE ports and that each port's PoE standard can power the highest-watt device.
Is a 60 W PoE switch enough for 4 cameras?
Often yes for four typical fixed IP cameras around 6-10 W each, especially with PoE+ ports. It may not be enough if the cameras have heaters, infrared, motorized zoom, or PTZ functions, so use the camera's maximum power draw.
What is the difference between PoE, PoE+, and PoE++?
PoE usually refers to 802.3af, PoE+ to 802.3at, and PoE++ to 802.3bt. The higher standards can provide more power per port, which matters for high-power access points, PTZ cameras, displays, and specialty devices.
Should I use device watts or switch allocated watts?
Use device maximum consumption if you are planning from data sheets. If your switch already reports allocated watts per port, that number may already include PoE class allocation, so avoid adding a large cable-loss allowance twice.
How much spare PoE budget should I leave?
A 20% reserve is a practical starting point for small networks. Use a larger reserve when devices have heaters, motors, high infrared load, future expansion, or unknown startup behavior.
Does cable length affect PoE power budget?
Cable length and cable quality can affect voltage drop and losses, especially near the per-port limit. This calculator uses a cable-loss allowance for planning, but long cable runs should still follow the device and switch installation limits.
Can a PoE+ switch power normal PoE cameras?
Usually yes. A PoE+ switch can normally power lower-power 802.3af devices as long as the switch supports the device mode and has enough total PoE budget.
Why does my PoE switch say enough watts but a device will not power on?
The total budget may be enough while the per-port standard is too low, the port is not actually PoE-capable, the cable run has problems, the device uses passive PoE instead of standard PoE, or the switch has a per-port allocation limit.