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Is ZigBee or Wi-Fi More Cost-Effective and Efficient for Smart Grid Communications in the Home?

A newly published GE white paper finds that, between two popular technologies for home area network (HAN) communications, ZigBee is at least two times more cost-effective and efficient than Wi-Fi.

Today GE will release a white paper that declares ZigBee the winner of the energy-efficiency contest between two wireless technologies for home area networks.

GE Brillian Nucleus photo on EnergyPriorities.com

GE’s Nucleus home energy command center with Brillion technology combines Wi-Fi and ZigBee communications capability. Nucleus is expected to be available for consumer purchase in early 2011 at an estimated retail price of $149-$199.

"Energy Efficiency Comparisons of Wireless Communication Technology Options for Smart Grid-Enabled Devices" says the two technologies that best meet the overall performance and cost requirements for HAN communications are Wi-Fi and ZigBee.

GE Appliances & Lighting says it evaluated how much energy each of the technologies consume under typical residential smart-device conditions and in a configuration representative of future mass-production implementation.

On average, GE found the ZigBee system consumed less than half as much energy as the Wi-Fi solution:

"The testing under identical conditions in a smart appliance communications module revealed that a ZigBee system consumed an average of 0.39 watts over a 24 hour period, while the Wi-Fi system consumed more than twice (2.2 times) the power of the ZigBee solution, a total of 0.87 watts over the same period."

Why energy consumption in wireless devices matters

As the smart grid extends into homes, the potential energy-saving benefits are significant. Rewiring homes for sensors and switches would be expensive, so wireless alternatives have emerged to meet the communication needs of the smart home.

Most wireless devices operate on batteries, which must be changed if the system is to continue operating. (How's the battery in your smoke detector? Imagine having 20 more of them in your home.)

The communications technology inside a wireless network must consume as little power as possible. Because of their widespread use at the residential level in home area networks and in smart devices, the choice of technologies is important. In the white paper, GE says it anticipates there will be 750 million to 1 billion smart, connected devices in the U.S by 2017.

By projecting ZigBee's lower device-level power consumption to the anticipated installed base, GE estimates significant aggregate power savings (370 megawatts) and yearly energy cost savings for consumers ($315 million) compared to Wi-Fi.

What's the difference between protocols?

Wi-Fi (IEEE 802.11/n) is widely used in data networking -- it's entirely likely you're accessing the internet over Wi-Fi now. It is an open protocol, so manufacturers can incorporate Wi-Fi into their devices without licensing it. GE's Digital Energy division incorporates Wi-Fi into automated meter infrastructure products, which maintain communication between utilities' data-gathering networks and millions of smart meters. GE also builds Wi-Fi into various healthcare products.

ZigBee (IEEE 802.15.4) is a wireless protocol developed for commercial building automation. 350 manufacturers have officially adopted ZigBee, building it into 100 products to date. Licensing the ZigBee protocol requires membership in the ZigBee Alliance. The 176 top-level supporters and participants in ZigBee include Whirlpool, Philips, Intel, Cisco -- and GE.

Jeff Drake, advanced systems engineer for GE Appliances, and co-author of the white paper, is an IEEE member participating in the 802 standard series that encompasses ZigBee, and is an active editor for the ZigBee Alliance Smart Energy profile.

There are other wireless technologies designed for residential energy management systems. Z-Wave is a wireless mesh networking protocol established in 2005 and has the support of about 150 consumer product manufacturers. Certified Z-Wave products are currently available in 400 devices. The relatively recent enOcean technology includes extremely energy-efficient radios and sensors that are self-powering. By "harvesting" energy from the surrounding environment, these wireless devices operate without battery changes. GE did not compare enOcean or Z-Wave devices for its white paper, but the Association of Home Appliance Manufacturers published a detailed evaluation of these and other technologies including OpenADR, Bluetooth and HomePlug.

Do vendors and installers have to choose one technology?

The choice of a single "winning" protocol is not standing in the way of widespread development of products for home automation and energy monitoring. If home builders and remodelers install one of the popular technologies in homes, it won't close the door to future enhancements for those homeowners.

When push comes to shove (if it hasn't already), a household protocol converter could serve as a translator. At a unit cost of a few dollars for wireless communications chips, manufacturers could also offer multi-protocol devices. An example is a smart meter that uses Wi-Fi to communicate with the utility, and both Wi-Fi and ZigBee to communicate with sensors and switches within the home.

Even GE hasn't hung its hat on a single protocol. Dave Najewicz, manager, external technology programs, GE Appliances and one of the paper's co-authors, clarified in an e-mail:

"While GE does support ZigBee as the emerging wireless standard for connecting devices within the home, GE’s Nucleus energy manager with Brillion technology does contain a Wi-Fi communications capability (in addition to ZigBee)," Nejewicz says. "However, for appliances within the home, GE's position is that ZigBee ( SEP 1.0/2.0) does represent the future standard for home area networks, and that is reflected in GE’s Profile smart appliances with Brillion technology and other products (programmable thermostats, pool pump controls, 120V/240V switches, EV charging stations) that GE is currently developing. To date, none of these GE products utilize Wi-Fi communications technology within the home."

DOWNLOAD the GE white paper "Energy Efficiency Comparisons of Wireless Communication Technology Options for Smart Grid-Enabled Devices."


Public companies: General Electric (NYSE: GE)