Energy management—Making the most from available technologies and how to deal with increasing plug loads
The migration of energy management from the margins of the commercial buildings sector to the mainstream has produced even greater reductions in energy intensity.

October 2017 — The American Council for an Energy-Efficient Economy defines energy management as the “systematic tracking and planning of energy use that can be applied to equipment, buildings, industrial processes, industrial or institutional facilities, or entire corporations. A thorough energy management program consists of metering and monitoring energy consumption, identifying and implementing energy-saving measures, and verifying savings with proper measurements.”

Energy Management Technologies

The development of more stringent codes and standards for commercial buildings, like the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 90.1, has accelerated adoption of these energy management technologies.

Government policies and programs, as well as a range of reporting requirements, have also encouraged adoption of energy management tools in commercial buildings. Buildings encompass a constellation of individual components and systems with different operating parameters and independent control systems.

Energy management information systems provide hardware and software solutions for monitoring building energy consumption. Examples of these solutions include:

  • Data acquisition hardware such as submeters and utility meters
  • Formal energy management systems
  • Combinations of monitoring and control capabilities applied to base building systems
    • HVAC
    • lighting
  • Exported energy data from building management systems

Data in the various systems can be normalized against weather, user behavior, and other variables to better indicate consumption trends and the impacts of efficiency measures. The development of advanced energy management systems over the past two decades has enabled even larger gains in the energy performance of building base-systems loads.

Plug Loads and Energy Management

While base building systems have become more efficient, plug loads have generally been increasing. Plug loads refer to electric power consumed by products through an ordinary alternating-current (AC) electric wall socket. Plug loads now account for 15 percent of all residential electricity consumption and 20 percent of commercial consumption.

The primary change in building energy consumption projections for the next decade is an accelerating shift from base systems to plug loads as the largest source of energy consumption.

Plug-Load Challenges

Although the definition may be construed more or less broadly, plug loads are generally considered to pose a different challenge than base systems. The proliferation of new plug loads, ranging from clocks and computers to smartphones and cable boxes, has shifted the flow of energy through the built environment. Not only has the scope of electric equipment expanded in recent years, but the scale of energy consumed by these device loads also has exploded.

Plug loads account for roughly one-third of all electricity used in a typical office building in California, according to a survey of plug loads commissioned by the California Energy Commission and performed by ECOS Consulting. The survey concluded that California’s office plug loads consume more than 3,000 gigawatt (GW) hours of electricity and cost business owners over $400 million annually. The associated CO2 emissions of these plug loads is more than 770,000 tons (635.03 million kg) annually—equivalent to the CO2 emissions of 140,000 cars during one year. Computers and monitors accounted for about two-thirds of the total plug-load energy use in office buildings. In addition, common office electronic devices such as printers, faxes, and computer speakers accounted for an estimated 17 percent of plug-load energy use. Miscellaneous devices such as portable lighting, telephones, and coffeemakers made up the remaining 17 percent.

Plug-Load Analysis

In an analysis of plug loads, E Source, an energy-efficiency consulting firm based in Boulder, Colorado, surveyed hundreds of data sets from multiple independent sources and identified the most significant plug loads based on average annual energy consumption and total power draw by operating mode. The effort also produced some interesting facts and statistics about plug loads:

  • In the home, set-top cable boxes consume about as much energy annually as a refrigerator
  • In the office, high-capacity color copiers are among the largest common plug loads
  • Typical plug-load culprits include
    • Computers, monitors, speakers, and task lighting
    • Chargers for phones, tablets, laptops, and other handheld or portable devices
    • Printers, copiers, scanners, fax machines, and multifunction devices
    • Coffeemakers and water coolers
    • Vending machines, refrigerators, and other appliances
    • Servers

E Source also identified the ten largest power-drawing plug loads while in active mode and the five largest energy-consuming plug loads while in idle mode over the course of an entire year. In the active-mode category, common kitchen appliances like toasters and microwaves account for many of the most energy-intensive plug loads in active power mode.

In many instances, new electronic devices are engineered to allow reduced electricity use in lower power modes, so switching devices from higher power mode to lower power mode is an easy way to save energy. But the best way to save energy is to ensure devices are turned off or unplugged when not in use for extended periods or at the end of the day.

Many electronic devices use significant amounts of power when they are in sleep or idle mode. Devices that use power in sleep or idle mode are commonly called “phantom” or “vampire” loads. A typical US home has about 40 “phantom” energy products continuously drawing power, including mobile-phone chargers, cable boxes, computers, and game consoles.

As stated earlier, plug loads now account for approximately 20 percent of electricity use in commercial offices. Studies have shown plug load devices to be the fastest-growing segment of commercial and residential electricity consumption. As improvements continue to be made to HVAC and lighting efficiency, office plug loads are consuming a more significant share of commercial electricity.

Plug-Load Assessment and Reduction Strategies for Building Professionals

Reducing the amount of plug-load energy consumption in a building or portfolio of buildings starts with an assessment and reduction strategy. The following are suggested processes:

  • Measure baseline plug-load energy use.
  • Establish a reduction metric.
  • Obtain stakeholder buy-in.
  • Create a change management plan to engage tenants.
  • Review plug load equipment and create an electronic inventory log.
  • Unplug any unused and unnecessary equipment.
  • Recycle unused and unnecessary equipment.
  • If purchasing new, research and purchase the most energy-efficient equipment.
  • Create and implement strategies to turn off equipment when not in use.
  • Consider energy reduction contests to further engage tenants.
  • Measure plug load and energy use after reduction measures are put into place or practice.
  • Communicate energy savings to stakeholders and tenants.

This article is adapted from BOMI International’s High-Performance Sustainable Building Principles, part of the new High-Performance Sustainable Buildings credential (BOMI-HP™). More information regarding this course or the BOMI-HP™ credential is available by calling 1-800-235-2664. Visit BOMI International’s website, www.bomi.org.