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What is Power over Ethernet (PoE)?

January 24, 2022

Power over Ethernet (PoE) Explained

Power over Ethernet (PoE) delivers power and data over standard Ethernet cables (also known as category cables, or CAT series cables - i.e. CAT5). You likely interact with PoE technology everyday, and don't even know it! Common devices that use PoE are VoIP telephones, Wi-Fi routers, and security cameras, but other devices (like lighting systems) can be retrofitted to be powered by PoE. PoE was invented initially to reduce the number of necessary cables from two (one cable for power, one for data) down to one (just one cable that can transfer both power and data).

If you were online in the early 2000s, before Wi-Fi was mainstream, you probably remember having to use ethernet cables to connect to the internet. However, they are not an outdated piece of technology at all, on the contrary, ethernet cables are poised to make a massive comeback in the mainstream tech scene. In fact, according to Fortune Business Insights, the global PoE LED lighting market size is projected to reach 544.8 million units by 2026, so it’s becoming an increasingly popular technology.

ethernet cable

Power over Ethernet was initially designed to deliver power to VoIP (Voice over IP) office phones. Due to the bandwidth efficiencies and low costs that VoIP technology provided, there became a clear advantage of using a digital IP network versus a traditional analog telephone network for office telephony, but this posed the new challenge of powering the phones. In traditional land line setups (using RJ11 Connectors) A.K.A the public switched telephone network (PSTN), power is also delivered over the telephone cable (about 52 Volts DC, depending on your telephone service provider), with just enough current to make your phone ring or light up. On the other hand, VoIP phones are digital and need a bit more juice to operate, specifically about 10 watts, but they couldn't get this power from the traditional Ethernet (RJ45) connections (at least not yet!). This problem became increasingly important to solve as more customers wanted the flexibility of a VoIP setup, but needed a better way of getting power to their phones. In the late 90's and early 2000's Cisco rushed to lead the VoIP market by inventing the first.

"proprietary version of PoE in 2000, to enable scalable and manageable power delivery to Cisco IP-telephony handsets."

Cisco's version of the story can be found on their "What is PoE" page.

This marked the beginning of the rise of PoE. Since the early 2000's PoE has been generally divided into two buckets: ad-hoc or proprietary solutions (like Cisco's initial implementation) and standardized solutions. The standardized solutions have been largely managed by the IEEE (Institute of Electrical and Electronics Engineers), specifically by the IEEE 802.3 Working Group. These standards group PoE into 4 different types (or standards) and 8 different classes (of power). These classes and types can be seen in the table below (pulled from the PoE Wikipedia article):

4 Different Standards of PoE Power

table depicting all the different PoE standards

To help you understand the above table, the following terms are handy:

PD (powered device): This is any device that receives its power through PoE. This includes a vast array of devices such as: VoIP telephones, Wi-Fi routers, security cameras, monitors and displays, PoE light fixtures, POS (point of sale) terminals, etc.. There is also a type of PD called  a PoE splitter. A PoE splitter essentially splits the power from an incoming PoE line into two separate outputs; one Ethernet port for data only and one low-voltage DC power output (this is useful for devices that are not PoE compatible, but still need power and data).

PSE (power sourcing equipment): This is any device that sends power along Ethernet cables. This includes PoE switches, PoE injectors, and PoE midspans.

Latest Developments

The most exciting developments to standardized PoE (in our opinion) are the type 4 PoE (IEEE 802.3bt - 100W) and the IEEE 802.3bu single pair Ethernet (SPE) PoDL (Power over Data Line) standards. Type 4 (100 W) PoE is interesting because it enables a whole new class of devices to be installed using PoE (namely LED light fixtures). SPE is interesting because it has the potential to dramatically reduce cable costs, because these cables have only a single pair of copper conductors, versus the 4-pairs in standard (CAT series) Ethernet cables.

What are the benefits?

Put simply: Energy savings (through increased power efficiency and automation) and installation cost reduction. Power over Ethernet transmits low-voltage DC (direct current) power, and converts from AC at one single point (usually very high efficiency - typically 95%) which eliminates the need to convert high-voltage AC into low-voltage DC at the point of load, which is typically inefficient (~60%-90% on average). This conversion that takes place with traditional systems, wastes energy and money, meaning a grid based on PoE can help your building reach carbon emission goals and reduce energy costs. You can estimate savings potential using this calculator we built!

The design and installation of a PoE system is also typically simpler and quicker than standard (AC) electrical systems. The system is simple to retrofit into most buildings, and requires less electrical expertise. Again, creating the potential to save money for both electrical upgrades and new installations.

What About the Electrical Codes?

A lot of the hype surrounding PoE was due to many on-lookers thinking that they could save on electrical installations, by getting network installers to install PoE lighting versus paying a licensed electrician or contractor to complete the job. The hype was understandable, because the installation cost difference can be dramatic in many scenarios. However with lighting, the safety risk is not just in the electrical connections, it's also with how the fixtures are secured to the ceiling (so they don't fall, especially in the case of a fire). The electrical safety authorities are quickly catching on to this - for example the ESA (Electrical Safety Authority) in Ontario, Canada has already updated their code book (OESC - Ontario Electrical Safety Code) to cover the installation of Type 4 PoE in the OESC, 27th edition - 2018. The specific additional rules covering PoE can be seen here (pulled directly from a purchased copy of the code book):

PoE rule 16-000 1 e)

PoE rule 30-1400

A PoE Hotel!

One of our favourite case studies for PoE use in buildings, is the retrofit of the Sinclair Marriott hotel in Fort Worth, Texas.

This case was nicely put in the story released by The Architectural Digest. Here is a small excerpt:

Like a lot of things in Texas, the Sinclair aimed for bigger and better, which resulted in becoming the first hotel in the world to power its lights, window shades, smart mirrors, and minibars with power over Ethernet (POE) technology. Ethernet cables are typically used as network communication lines for landline phones and routers, but Sinclair Holdings president and the hotel's developer, Farukh Aslam, discovered that Ethernet cables could be used in a more efficient way. “We are taking modern technology and maximizing its potential in The Sinclair, a 90-year-old building, while staying true to the quality and detail of its iconic design,” says Merriman Anderson Architects senior associate and team leader Patrick Hazard. When opening a previous hotel, Aslam installed a light dimming system that never worked. When the electricians couldn’t tell him why, Farukh looked for something more efficient, which is when he came across Cisco, the technology company that produces a POE lighting system with a dimmer built in. Thus began a new adventure into power over Ethernet.

PoE in the Cence Low-Voltage DC Microgrid (Cence LVDC)

At Cence we manufacture an intelligent DC microgrid that we market as SpacrGrid. Our DC microgrid is wire agnostic, but is compatible with Ethernet cables, which puts us in the bucket of Ad-hoc or proprietary PoE solutions, although we also have optional IEEE 802.3 standard compatibility. Our version of PoE allows for daisy chaining, and eliminates the need for a costly PoE switch (the data traffic is managed at each load, instead of at a switch).

The purpose of our microgrid is to reduce energy consumption in commercial and residential lighting and HVAC systems, typically by around 20%. This is accomplished by increasing the efficiency of power distribution and AC-to-DC conversions, collecting environmental data, and intelligently automating the control of all connected devices.

So it's clear that the future of power distribution is moving towards Direct Current (DC), and that PoE seems to be leading low-voltage power distribution technologies. We're probably not too far away from a future with PoE and USB-C wall outlets versus standard AC electrical sockets (hopefully)!
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Bolis Ibrahim

Bolis Ibrahim Is the CEO at Cence Power. He is a technology entrepreneur and engineer. He started his entrepreneurial journey with a small recording studio, then graduated onto a high growth tech startup, Argentum Electronics. The Argentum team has now merged with Cence Power, their mission is to conserve energy & CO2 emissions for buildings with patented DC (direct current) power distribution systems.

Cence Brings Buildings Into The Future

We improve the value of commercial and multifamily buildings with an intelligent DC power distribution system that's pain-free to install. It combines the benefits of low-voltage wiring practices with voltage capabilities of up to 450 Volts DC.

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