PoE Power Budget Calculator
What the PoE Power Budget Calculator does
The PoE Power Budget Calculator estimates the total Power over Ethernet output budget a network switch needs to supply a group of security cameras and other powered devices. It combines the cameras’ maximum power draw with any additional PoE loads and estimated cable losses, then accounts for the percentage of the switch’s budget you want to keep unused.
PoE lets a compatible switch send power and network data over the same Ethernet cable. This can simplify a security camera installation, but a switch must have enough power available for all connected devices. The Required PoE Budget result gives you an aggregate target in watts for comparing switches or reviewing an existing installation.
The result is an estimate of the switch’s PoE output budget. It is not the switch’s AC input power, an electricity consumption forecast, or a guarantee that every camera will work with a particular switch. Always check the specifications of the cameras, switch, and cabling before choosing equipment.
How to use the PoE Power Budget Calculator
Gather the maximum power requirements for your cameras and any other devices that will draw power from the same switch. Then enter the following values:
- Number of PoE cameras: Enter the number of cameras that will receive power from the switch. The calculator accepts whole numbers from 0 to 1,000.
- Maximum PoE draw per camera (W): Enter the maximum power draw, in watts, for one camera. Use the manufacturer’s specification and consider power-intensive features such as infrared illumination or a heater when they are included in that maximum.
- Other PoE loads and estimated cable losses (W): Enter the combined watts for other powered devices and any cable losses you have estimated. Examples of other loads include a PoE access point, doorbell, or network intercom.
- Unused budget headroom (%): Enter the percentage of the switch’s total PoE budget that you want to leave unused. The calculator accepts values from 0% to 80%.
Read the Required PoE Budget result in watts. When comparing switches, look for a PoE output budget that meets or exceeds this figure, while also checking the available ports and each port’s power capabilities.
The camera input assumes that every camera uses the same entered maximum draw. If your cameras have different ratings, a conservative approach is to enter the highest maximum for every camera. This can overestimate the budget, so account for that when reviewing the result. You can also include other known loads in the additional load field.
How the PoE Power Budget Calculator formula works
The calculator first estimates the total maximum load. It multiplies the number of cameras by the maximum draw per camera, then adds the other PoE loads and estimated cable losses:
Total load (W) = Number of cameras × Maximum draw per camera (W) + Other loads and estimated cable losses (W)
It then divides that load by the share of the switch’s budget you intend to use:
Required PoE Budget (W) = Total load (W) ÷ (1 − Unused budget headroom (%) ÷ 100)
For example, 20% headroom means the estimated load should use 80% of the switch’s total PoE budget. Dividing by 0.80 finds a budget that leaves the requested share unused. This differs from simply adding 20% to the load: adding 20% would leave a smaller proportion of the resulting budget unused.
Worked example using the default inputs
Assume you have eight cameras, each with a maximum draw of 12 W. You also allow 10 W for other PoE loads and estimated cable losses, and you want 20% of the switch’s budget to remain unused. These values are illustrative assumptions; replace them with figures appropriate to your installation.
- Camera load: 8 × 12 W = 96 W
- Total load: 96 W + 10 W = 106 W
- Usable share of the budget: 100% − 20% = 80%, or 0.80
- Required PoE Budget: 106 W ÷ 0.80 = 132.50 W
In this example, a switch needs an aggregate PoE output budget of at least 132.50 W to support the assumed load while keeping 20% of its budget unused. A switch with a higher available budget may be appropriate, provided its ports and PoE standards also meet the devices’ requirements.
Use cases for the PoE Power Budget Calculator
Planning a home security camera system: Estimate the budget for a new switch before installing cameras around entrances, driveways, or other areas. Using each camera’s maximum specified draw helps you plan for conditions that may consume more power than normal daytime operation.
Expanding an existing installation: Recalculate the total when adding cameras to a switch that already powers other equipment. Include the existing powered devices and estimated cable losses in the additional load field.
Comparing PoE switches: Use the result as an aggregate wattage target when reviewing product specifications. A switch may have enough Ethernet ports for your devices but still have an insufficient total PoE budget.
Allowing room for future changes: Enter an unused headroom percentage if you want some budget to remain available. The percentage provides a buffer in this calculation, but it does not replace a separate estimate for devices you already plan to add.
Checking a mixed network: Cameras are not always the only devices drawing power from a switch. The additional load field lets you include the combined estimated demand of other PoE equipment on that same switch.
Other factors to consider when calculating Required PoE Budget
Per-port power limits matter. A switch can have a sufficient total PoE budget and still be unable to power a particular camera if the connected port cannot supply enough power. Check the maximum output of each relevant port against the device’s requirements.
Confirm PoE standards and compatibility. Review the standards supported by both the switch and each powered device. Devices with higher power requirements may need a compatible higher-power port. Do not assume that a port will support a camera simply because both products are described as PoE.
Account for cable losses. Power is lost as it travels through Ethernet cabling, and the amount varies with the installation. The calculator does not estimate those losses automatically. Include an appropriate estimate in Other PoE loads and estimated cable losses (W), using the information available for your equipment and cable run.
Use maximum device specifications. A camera’s typical draw may be lower than its maximum. Features such as infrared lighting, pan-and-tilt movement, or built-in heating can affect demand. Check the manufacturer’s documentation for the maximum applicable to your model and operating conditions.
Consider simultaneous demand. The calculation treats the entered camera maximums and additional load as a combined load. Actual demand changes over time, and devices may not all reach their maximum at once. Planning with maximum values can provide a conservative estimate, but the result depends on the figures you enter.
Check the available PoE output budget. Product descriptions may list a switch’s total electrical consumption or power supply rating alongside its PoE budget. Use the specified aggregate PoE output budget for comparison with the calculator result. Also check whether the published budget depends on a particular power supply or configuration.
Count powered ports as well as watts. The calculator estimates power, not port availability. Make sure the switch has enough compatible PoE ports for all devices that need them, along with any network connections your installation requires.
PoE Power Budget Calculator FAQ
What is a PoE power budget?
A PoE power budget is the total power a switch can supply to connected PoE devices, usually expressed in watts. It is shared across the switch’s powered ports. The total budget and the limit of each individual port both matter when selecting a switch.
How much headroom should I enter?
Choose a percentage based on your installation and how much of the switch’s budget you want to keep unused. For example, the default 20% is an illustrative assumption, not a requirement. Consider the accuracy of your device and cable-loss estimates, expected changes, and the switch manufacturer’s specifications.
Can I use the calculator for devices other than cameras?
Yes. Enter the combined power draw of other devices, along with estimated cable losses, in the additional load field. If there are no cameras, you can enter zero for the number of cameras and use the additional load field for the devices you want to include.
What if my cameras have different power ratings?
The calculator uses one maximum draw for every camera. You can enter the highest camera rating for all cameras to produce a conservative estimate, although that may overstate the total. Check each camera’s individual requirements and ensure its switch port can supply the necessary power.
Does the result include cable losses automatically?
No. The calculator includes cable losses only when you add an estimate to the Other PoE loads and estimated cable losses (W) field. Actual losses vary with the cable and installation, so check the relevant equipment and cabling specifications when developing your estimate.