PoE - Power Supply

Power Supply

When designing a PoE system, you will want to calculate how much power you will need. Calculating too much power can result in a larger and more expensive power supply than necessary, and it may even require a larger panel than originally specified. Underestimating can possibly damage equipment.

Traditional Calculation

To calculate the PoE Power requirement, you might try calculating with the following formula:

(PoE port quantity * port power available + PSE power requirement) + 20% buffer

Optimized Calculation

A more accurate calculation for PoE power requirement would include information about the PDs.

(PoE ports utilized quantity * port power used + PSE power requirement) + 20% buffer

Let’s say you have a PSE that supports eight ports at 30 W each, four PDs that are only 802.3af (15.4W) and four PDs that are 802.3at (30 W). We would lower our power budget by (30-15.4 W) * quantity of 802.3af PDs (4) + 20% buffer (70 W savings).

By utilizing the optimized calculation, we can save power requirements for ports that we know are lower powered.

Check out this cool video from Antaira that shows this concept!