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Building Manager Green Tip

January 2012

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Small Loads = Big Problem

Plug loads, the energy consumed by devices plugged into wall sockets and receptacles, are normally small when considered individually. However, in aggregate they can account for up to 18% of a typical building's electricity consumption according to data from the EIA's Commercial Buildings Energy Consumption Survey.    

Though such loads cannot be erased, there are a variety of tools available on the market today to allow building managers to monitor, trend, and manage plug loads to assist in ensuring that no energy is consumed unnecessarily.  

Please note that while many links are provided to equipment manufacturers below, these are provided for informational purposes only to show a representative sample of available technologies.  Harvard University and its affiliates do not specifically endorse or recommend any of the products listed in this newsletter and may not be used in commercial or political materials, advertisements, emails, products, promotions that in any way suggests approval or endorsement of Harvard University.


Multiple vendors offer equipment that allow plug loads to be monitored.  By learning more about which devices are consuming the most energy, it's possible to develop a management strategy that targets the equipment with the greatest potential for reductions.  

  • Basic Plug Monitor - Plugs into the wall and monitors a single device over time on the device only (i.e no exporting a computer).
  • Plug Monitor with Trending - Similar to the basic plug monitor, but capable of exporting trend data via USB to a computer for greater analysis.
  • Power Strip Monitor - Similar to the monitors above, but in a powerstrip form with 10 grounded outlets for monitoring combined computer or AV setups. Alternatively, it's often possible to simply plug a powerstrip into one of the more basic monitors listed above.
  • Professional Energy Consumption Monitor - Not recommended for users only looking to track consumption in a single space, this professional system uses a standard meter that can connect to a system of interchangeable CTs capable of monitoring everything from individual loads to entire electrical panels, including  240V service and "certain 3-phase loads".  

Timers and Smart Power Strips

Once you have a good understanding of how your equipment is consuming energy, there are many options for devices capable of shutting power off based on schedule, occupancy, or other triggers.

  • 24 Hour Plug Timers - Starting around $5, these basic timers are typically analog and capable only of shutting power on and off based on a schedule that is the same every day, limiting its applicability in environments where weekend schedules are different than workdays.
  • 7 Day Plug Timers - Similar to the above, but capable of setting weekly schedules instead of daily schedules only.
  • Smart Power Strips - Designed for computers or AV devices, these smart power strips shut power to all peripheral equipment (e.g. printers, speakers, monitors, DVD players, etc.) when they detect a master device (e.g. a computer or tv) has turned off, regardless of the time of day or schedule.
  • Occupancy Sensor Strips - Similar to the Smart power strip, these units are controlled not by a master device but by an attached occupancy sensor that can detect whether occupants are in a room or at a desk.

Comprehensive Plug Management Systems

Modlet plug load monitoring and management device.

While the equipment above typically either monitors plug loads or manages them, there are some manufacturers who have developed comprehensive systems that perform both tasks and can be coordinated across entire spaces or buildings instead of outlet by outlet.

  • Modlet - This comprehensive monitoring and management system features devices that plug into the wall (pictured above) that wirelessly report consumption data to computer outfitted with a USB receiver.  In addition to near real-time reporting and trending, it is possible to set shut-off schedules for each device independently or as a group from any point connected to the internet via online accounts.  
  • Smart Circuit - Instead of a device that plugs into existing outlets like the Modlet, these devices are hard-wired into the circuit between the circuit breaker and the outlet, making them more suitable for new construction or larger retrofit projects. They are web enabled and feature both monitoring and management capabilities.  In addition to schedule based controls, it is possible to set these up to automatically shed loads in a controlled manner once peak consumption thresholds are exceeded.

Green Building Services provides consulting services to ensure that the design, construction and operation of Harvard's built environment has minimal environmental and human health impacts, maximizes occupant comfort and generates an awareness of sustainable design and building operations. To learn more about our work and services, visit http://green.harvard.edu/gbs.