Clarity begins at home: CEE turns microscope on itself for plug load study

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CEE’s research team explores and identifies cost-effective energy efficiency measures to improve utility programs and related policy efforts. We conduct field research in buildings, ranging from homes to high-rise office towers, analyzing valuable data on the energy savings and performance characteristics of energy upgrades. Among our recent projects, CEE’s team is looking into commercial building plug load energy use and evaluating reduction strategies through control technologies (the systems and devices that monitor and manage a building’s operations) and occupant behavior strategies.

“Plug load” is the energy used by products that are powered by means of a standard electrical plug. Plug loads represent the fastest growing increase in energy consumption in U.S. commercial buildings, in stark contrast to decreases in other end uses such as cooling and lighting. This project investigates commercial building plug loads and evaluates various reduction strategies: two types of smart power strips, computer power management, and a behavior campaign.

Practice what we preach

This spring, as we finished our field work at offices around the metro area, we decided to practice what we preach and put our field work in action here at CEE. We added CEE’s downtown office as one last test site to answer the question, “Can we achieve optimal plug load savings at CEE?”

At all previous sites, we tested each strategy (smart power strips, computer power management, and a behavior) individually, assigning different strategies to participants without their input. At CEE we initially implemented computer power management with all participants, and after a few weeks we doubled the reduction strategy by adding a smart power strip at each workstation. Throughout the study we worked with two different types of smart power strips — one with an occupancy sensor and the other with a foot pedal. At CEE, unlike at the other sites, we allowed participants to choose which type of power strip they wanted installed at their desk. We hoped to find out if providing participants with a choice would increase satisfaction rates and overall savings.

Field work in action

Like at all sites in this study, we began by taking a few weeks of baseline measurements. Then our IT team implemented computer power management at designated desks. The computer power management settings that we used follow the ENERGY STAR Guidelines, which include putting monitors to sleep after 10 minutes of inactivity and desktop computers to sleep after 30 minutes of inactivity. We chose to first implement computer power management at CEE because preliminary results from the first few sites indicated that it offered the highest level of savings. Reactions from office participants were mixed — some people didn’t even notice the change and others saw a noticeable difference in the time it took their computer to wake up after they came back to their desk. Despite these differences, 77% of participants gave a positive response when surveyed about the measure.

Smart power strips were next. We installed the smart power strips in addition to the computer power management. Computer power management settings achieve energy savings from computers and monitors, and power strips address other desk plug loads from things like lights, radios, and fans, so they work well in tandem. This was different from other sites where we tested the strategies individually.

CEE participants had the option to choose between two smart power strips. The first was a power strip that could be activated by an occupancy sensor that would turn off outlets after 10 minutes of inactivity. The second had a foot pedal that could be used to activate and deactivate outlets. Once activated by foot pedal, outlets remain active for 10 hours or until the foot pedal is used to turn them off.

Each option had its benefits. No user interaction is required with the occupancy sensor, seen as a benefit by some participants and a drawback by others. Many selected the power strip with the foot pedal specifically because it offered more control. Of the 26 participants, 16 chose the foot pedal and 10 chose the occupancy sensor.

Now what? At other sites, where participants were not invited to choose their type of power strip, power strips achieved an average of 19-22% savings.

We had high hopes that by combining the two strategies and offering participants a choice of power strips we would see an increase in savings. But just how much energy did we save at CEE?? Check back later this year to see the results in our final report.

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