PoE Voltage: The Ultimate Guide
Power over Ethernet (PoE) is a transformative technology that has fundamentally changed how devices are powered and networked. By allowing Ethernet cables to deliver both power and data simultaneously, PoE+ voltage enables greater simplicity in connecting and operating devices like IP cameras, wireless access points, IP phones, access control systems, and IoT hardware.
Read on for an extensive guide exploring everything about PoE voltage across standards, influencing factors, device power optimization, and frequently asked questions. Let’s learn what voltage is PoE.
What Voltage is PoE?
On a basic level, voltage refers to the electric force or electric potential difference that powers electronic devices. It is measured in Volts (V). Higher voltage enables higher capacity to deliver more power. PoE voltage specifically indicates the electric potential transmitted over Ethernet cabling to provide the necessary power to devices on the network side.
Common PoE voltages generated from switches, injectors, and splitters range from 48V, 56V to even 60V, depending upon the type of PoE standard being used. PoE voltage is important for high-end PoE devices, such as the Reolink Duo 3 PoE, which is a 16MP dual-lens PoE security camera.
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PoE Standard Voltages
In order to promote interoperability of PoE capabilities and prevent voltage mismatch issues when connecting varied devices from multiple vendors, standard PoE voltage has been defined by the Institute of Electrical and Electronics Engineers (IEEE).
These help device manufacturers and PoE voltage infrastructure builders conform to certain power levels and voltage ranges. There are a few relevant PoE standards voltage specifying fairly precise voltage ranges:
PoE Voltage
The original IEEE 802.3af-2003 PoE standard voltage specifies supplying between 44 and 57 Volts DC over Ethernet, with a maximum power output of 15.4 Watts (W) per port. This means networked devices can draw up to 15.4W safely as the voltage will stay within the 44V to 57V range.
PoE+ Voltage
An update to IEEE 802.3af specification, IEEE 802.3at-2009 or PoE+, enhanced the power capabilities by delivering higher power 400mA at 52V to 57V levels while still using just the Ethernet cable.
Instead of only up to 15.4W earlier, the improved PoE+ could now transmit a max of 30W per port. This enabled support for a more advanced set of devices with higher power requirements compared to PoE voltage standard.
PoE+++ Voltage
Further improving upon existing specifications, IEEE 802.3bt-2018 or PoE+++ increased the voltage levels up to 60V in order to deliver even greater power capacity over the Ethernet cable.
By leveraging all four cable pairs together with higher power levels, the latest PoE+++ expanded the total power budget to a massive 90W device support on a single port, nearly 6X over the original 15.4W PoE.
Influencing Factors on the PoE Voltage Range
While PoE standards do define permitted voltage ranges, the actual voltage output exhibited by injectors/switches and, consequently the supply received by the powered devices can vary within the specified minimum and maximum levels due to diverse environmental conditions. Key aspects influencing PoE voltage ranges include:
PoE Standard
The predominant factor determining possible PoE voltage is the actual generation standard supported by the PoE switch, powered device, or injector being used in the infrastructure. As discussed in the previous section, 802.3af, 802.3at and 802.3bt standards define different voltage ranges like 44-57V, 52-57V, and up to 60V, respectively, according to power capacity.
Device Power Requirements
Networked devices can differ considerably in their power needs, which impacts voltage delivered accordingly. A basic IP phone may only consume 5W, while enterprise wireless access points with multiple high-gain antennas could utilize the full 15.4W capacity of older 802.3af PoE voltage switches.
Cable Length
Increased cable run means greater power loss during transmission through the Ethernet over distance. Resistive losses occur over longer lengths of copper cabling between the PoE source and powered device, resulting in some voltage drop accordingly.
Cable Quality
Along with cable length, the construction material consistency and resulting quality of Ethernet cables also impact sustained voltage levels. Poor quality patch cords tend to lose more power across the wire runs from source to device end even across the same distances compared to standards-grade Cat5e, Cat6, or above cabling.
Environmental EM Interference
Beyond cable quality itself, surrounding environmental conditions also impact sustained voltage. As mentioned earlier, laying cables near strong electrical sources or industrial motors can induce interference on unshielded copper Ethernet wiring.
PoE Voltage 12V for Different Devices
While the majority of enterprise PoE deployments leverage 48V power delivery derived from standards, certain devices operate at lower DC voltages. This requires additional PoE voltage 12v components for converting between voltages like:
12V PoE Injector
Alongside regular 48V PoE injectors, certain 12V PoE injectors take normal AC wall outlet electricity and convert it to a much lower stepped-down potential of 12V DC instead of the more common 48V.
PoE Switch Voltage
Recognizing the occasional need for 12V devices beyond standard 48V PoE, some advanced PoE switches meant for retail, industrial, or similar deployments offer select ports with 12V outputs.
12V PoE Splitter
As the name suggests, a PoE splitter device takes in the higher 48V PoE signal from the Ethernet cable and splits or divides it into separate 12V and 36V streams. The splitter has outputs to connect 12V devices on one side and 36V-powered equipment on the other simultaneously.
How to Optimize Device Power with PoE Voltage Output
While PoE standards already define working voltage ranges, further tuning output levels within specified limits provides maximum efficiency from deployed PoE infrastructure:
1. Use Thick 22AWG Minimum Ethernet Cables up to Necessary Length
Thinner Ethernet cables tend to lose more power across their length from the PoE source to the powered device, restricting reliable voltage. 22AWG bulk cable or higher thickness 23AWG patch cords help reduce resistive losses during transmission. Combined with minimizing cable length to only necessary runs avoids excess voltage drops.
2. Utilize Shielded STP Cables Near Electrical Lines
Unshielded UTP Cat5e/Cat6 cables laid in proximity to electrical lines, motors, or generators can pick up electromagnetic interference inducing fluctuations in PoE voltage output levels. Choosing shielded STP cables prevents erratic voltage and maintains steady power delivery even when running near electrical sources.
3. Install PoE Switches or Injectors Closest to Powered Device
By placing the power sourcing equipment (PSE) like PoE switches or injectors nearby the powered device (PD) instead of 100 meters away, voltage drop across the interim Ethernet cable gets minimized from resisting cable losses. Shorter cable length sustain better voltage.
4. Confirm Switch/Injector PoE Class Matches Device Needs
IEEE standards define various PoE Classes from 1 through 4 for different power levels - Class 1 = 4W, Class 2 = 7W, Class 3 = 15.4W, and Class 4 = 30W. Connecting say a Class 4 PTZ camera to a lower Class 1 PoE switch port can lead to rebooting or malfunctioning due to power starvation. Matching Classes prevents issues with the PoE output voltage.
5. Use Plenum CMP Cables in Ceiling Spaces
When mandated by building fire safety codes, using UL-listed 'CMP' marked Cat5e cables or above allows running through indoor ceiling plenum areas above drop ceilings safely due to low smoke and zero halogen jacketing. The thick 23AWG insulated twisted pairs maintain voltage better across long conduit runs up to 330 ft.
6. Upgrade to 802.3bt PSEs for Future Devices
As newer video analytics systems, machine vision gear, and IoT endpoints keep requiring greater than 30W power, proactively installing 802.3bt Type 3 and Type 4 PSE switches, splitters, and injectors ensures support through 90W capacity for next-generation smart building devices.
FAQs
Does PoE support 12V?
While PoE standards like 802.3af, 802.at, and 802.bt specify higher ~48V levels, specialized lower voltage PoE injectors, multi-voltage switches, and splitters do provide stepped-down 12V DC output to selectively power suitable PoE endpoints.
What current and voltage is PoE?
Under the popular 802.3af PoE standard used across verticals, voltage ranges from 44V to 57V DC delivered over Ethernet cable, supporting up to 15.4 watts of power. The maximum permitted current under 802.3af is 350mA, while higher capacity 802.3at and 802.3bt standards facilitate greater power throughput.
Is PoE 12V or 48V?
Standard PoE primarily operates at 44 to 57 Volt DC levels for power capacity ranging from baseline 15.4 watts to the latest 90-watt 802.3bt switches.
Conclusion
We have now covered PoE voltages extensively across relevant standards, device needs, and cable transmission aspects. The key takeaway is that delivering power over Ethernet cabling can involve various DC voltage levels primarily around 48V, with enhanced specifications and equipment now extending up to 90 watts device support. Additional components can also interface 12V PoE endpoints when needed.
Have you ever noticed specific PoE voltage before? Please share your experiences with us in the comment section below! Let's discuss together!
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