By Jonathan Marshall
Would you be satisfied with your home if its energy use fell only a third when you were away? Probably not, but that’s how most office buildings behave. That’s because employees often leave computers, printers, desk lamps, break-room appliances and other so-called “plug loads” running around the clock.
As companies upgrade to energy-efficient lighting and temperature control systems, the residual energy-saving opportunities from plug loads will loom ever larger, notes Steven Lanzisera, an energy analyst at Lawrence Berkeley National Laboratory (LBNL). In fact, such loads will likely represent close to 30 percent of U.S. building site energy use by 2030, according to LBNL estimates.
Lanzisera spoke on Tuesday to medium and large commercial customers at a PG&E-sponsored seminar on energy solutions in Oakland. He has unique insights based on a long-term study of plug loads at a 90,000-square-foot building on LBNL’s campus, which houses about 450 regular occupants. In temperate spring months, when air conditioning is turned off, plug loads account for 40 percent of the building’s entire electricity consumption.
At first glance, the number of different plug loads in such a building “makes your head spin,” Lanzisera says. They include portable fans, paper shredders, coffee makers, electric staplers, and wireless headsets. “There are so many kinds people don’t know where to get started,” he observes. “That’s one of major reasons people don’t address plug loads.”
But close inspection showed that more than three-quarters of energy use by plug loads at LBNL’s building was accounted for by IT equipment: computers (50 percent), computer displays and TVs (12 percent), printers and copiers (11 percent), and networking equipment (6 percent). And most of this energy was consumed during nights and weekends when employees were not using the equipment. That means the IT department is in a great position to implement office-wide energy solutions.
The first and simplest energy-saving remedy, Lanzisera says, is to make sure people buy only efficient products. Replacing an older 20-inch LCD monitor with a new EnergyStar-rated 24-inch monitor will increase usable screen area 44 percent while reducing energy use by a third. That’s practically a free lunch.
The second remedy is to tackle unnecessary nighttime loads with power management solutions. It turns out that the LBNL building’s computers draw substantial power—25 kilowatts—even late at night and early morning when almost no one is around. That’s almost 60 percent as much as they draw during normal business hours. Apparently many users don’t take advantage of their computers’ existing power management functions.
More than half of that off-peak energy use could be slashed by installing remote power management software that lets the IT department shut down or wake up computers by centralized commands. (That capability also gives the IT folks the capability to install remote backups and upgrades at night, when they don’t disrupt normal work.)
Lanzisera figures that such a solution would save about 150,000 kilowatt-hours per year, or 12 percent of the building’s entire annual electricity consumption. “Similar savings are probably realistic across many enterprises,” he says. And the other good news is that PG&E offers rebates of $15 per computer for the installation of power management software from qualifying vendors.
For many other plug loads, the simplest solution is to install smart plug strips, which use occupancy sensors, timers, or other mechanisms to turn devices on or off as needed. Such strips might save LBNL’s building a hefty 75,000 kilowatt-hours per year. Here, again, PG&E offers rebates of $15 for power strips activated by infrared or ultrasonic occupancy sensors.
If Ben Franklin were alive today, he’d probably title Lanzisera’s presentation, “A kilowatt-hour saved is a kilowatt-hour earned.” Taken individually, each plug load “just isn’t that much,” Lanzisera says. “In aggregate, however, across an organization, they can be quite significant and you can save a substantial amount of energy.”
Researchers like Lanzisera, and PG&E’s energy efficiency experts, are helping make such savings opportunities as easy and profitable as possible.
Email Jonathan Marshall at Jonathan.Marshall@pge.com.