Plug Loads A Growing Concern

May 7, 2013

And what can be done for better energy efficiency.

plugloadA recent study by the U.S. Energy Information Administration found that the fastest growing category in residential electricity usage is appliances and electronics—and many attribute this to our growing legions of electronic devices, chargers for mobile devices, and vampire or standby power, as appliances have generally become more energy-efficient.

The same is being seen in commercial buildings. In our recent posts on two of the greenest and smartest buildings in the world, the new Bullitt Center in Seattle and the Earth Rangers Centre for Sustainable Technology north of Toronto, plug load is being identified as a growing problem and one that must be addressed.

For the Bullitt Center, billed as the greenest office building in the world, an energy study prepared for the building showed that computers, monitors, laptops and IT equipment would use about one-quarter of the building’s electricity, while appliances, garage door openers, toilets, copiers and printers account for another 20 percent. (Lighting, even with a lot of daylighting and automated controls, accounts for 23 percent.)

The answer for controlling the energy use of individual computers, monitors, et al? The building will use Enmetric smart strips with separate occupancy sensors. Each outlet of  the Enmetric strips can be programmed separately to cut power when there’s no occupancy—or not, says Robert Pena, Associate Professor of the University of Washington’s Integrated Design Lab, which helped with the design of the building and will be monitoring its performance as one of the tenants.

The smart power strips by Enmetric will communicate via wireless ZigBee to a bridge, so every receptacle can be monitored. Eventually that may be bridged to a Climatec enegy monitoring system for the building.

Bullitt energy use

Reducing lighting and plug loads are big part of the energy savings needed to make the Bullitt Center energy self-sufficient.


At the Earth Rangers Centre for Sustainable Technology, manager Andy Schonberger is using energy management and monitoring systems from Schneider Electric to see, on his dashboard, that plug loads have been rising, to about 17 percent of the facility’s electricity usage. He’s looking to use the StruxureWare Energy Operations software the center uses for its dashboard to engage workers and tenants and give them warnings if the building’s energy usage is too high.

Energy Operations

“We are now looking at additional sub-metering to determine where this energy is being consumed,” Schonberger says, “Our plan is to break down these areas and add measurement points to six breaker panels currently not measured to provide a clearer picture on where this energy is being used and how best to deal with the increasing load.”

Plug Loads in Building Codes

Plug loads are starting to be addressed by commercial building codes as well. The latest ASHRAE 90.1-2010 building energy codes, upon which the new LEED v4 energy baseline will be based, require more aggressive plug load control.

The requirement under the ASHRAE code is that 50 percent of electric receptacles in a space have automatic shutoff control. These outlets can be governed by occupancy sensors or timers to cut power to computers, peripherals or other devices when occupants are no longer present.

“The idea is to get people used to using controlled receptacles and get the capability in buildings so users can start taking advantage of that,” says Eric Richman, senior research engineer for Energy Systems Analysis of the Pacific Northwest National Laboratory, which works on building codes.

Per DOE order, states are supposed to adopt the ASHRAE 90.1-20120 codes or a comparable code such as 2012 IECC by October 18, 2013. But don’t count on it. States may adopt codes in whole or in part, or with limitations. Jurisdiction and enforcement are also issues, as building codes are generally considered to come under local jurisdiction. Eventually, most states will adopt comparable codes.

Regardless, electricity use via plug loads, due to our legions of devices, is becoming more noticed and is starting to be addressed. It is no longer something that is just shrugged off as insignificant. And given our penchant for more and more devices, plug load will remain a growing concern.

 You may also like:

Greenest Office Building Sets a Standard for Energy Efficiency Tech

Energy Management Stars at one of the World’s Smartest Buildings

Beyond Earth Day: 10 Lasting Green Tech Trends

Are Smart Buildings Taking Off?

Big Data, Internet of Things Will Improve Efficiency and Profitability

‘Greenest Home in America’ Relies on Efficiency Technologies


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