Tackling Commercial Office Plug Load
Building owners and facility executives are always looking for new ways to control energy costs. Plug loads significantly impact an energy budget—sometimes accounting for as much as 50% of the total energy consumption in commercial spaces, and there are no-cost and low-cost solutions that can tackle the problem.
Plug load (sometimes referred to as receptacle load) is the energy used by devices that typically plug into an ordinary AC outlet. Devices such as computers, monitors, printers and servers typically are the biggest contributors to plug load but vending machines, coffee makers, cell phone chargers and kitchen equipment all contribute.
Plug loads are one of the fastest growing sources of energy use in commercial buildings today. The GSA estimates that offices contain an average of 7 devices per employee and 30 plug load devices per 1,000 square feet of office space. According to the New Buildings Institute, plug loads account for 15-20% of office electricity use and in offices that have already improved the efficiency of their lighting and HVAC systems, that number can be as much as 50%.
What is Plug Load Control?
Plug load control is the ability to limit the electricity used by equipment that is powered by an ordinary AC plug. The energy savings depends on a number of factors including power consumption characteristics of the contributing equipment, occupant behaviors, and automated controls including occupant sensing and time scheduling.
Here are several smart control strategies for controlling creeping plug load.
Occupant awareness and engagement - Employees aren’t the ones paying the utility bill, so they don’t realize how not turning off a task light or a computer monitor at the end of the day can impact their organization and the environment. Implement awareness programs including end-of-day reminders to shut off computers and individual task lights to help employees participate in reducing the load.
Remove or replace equipment - If a device is no longer used, remove it or at least turn it off. Replace older, required equipment with more energy-efficient and task-appropriate equipment. For example, laptops use less energy than desktop computers while also providing mobility, and LED monitors use less energy than CRT or LCD monitors. Consider ENERGY STAR labeled products monitored by the EPA and U.S. Department of Energy (DOE). Many commercial offices will find opportunity to save on their plug load energy usage by taking inventory of the equipment they have on-site as part of a formal energy reduction plan.
Leverage an advanced lighting control system - With an advanced lighting control system, smart control strategies such as time scheduling and occupancy sensing can be implemented to reduce plug load.
- Time scheduling aims to shut off lighting and controllable plug load during scheduled, non-business hours.
- Occupancy sensor controls further shut off these circuits when occupants are away from the controlled space during business hours.
Plugs are programmed to switch on/off based on a schedule or in response to an occupancy status signal from a sensor.
Energy codes are constantly updated and each update typically results in more stringent requirements. Energy consumption at the receptacle level is growing because the number of devices per square footage and/or employee is growing. These two facts combined, likely means automatic plug load control will continue to not only garner attention but requirements could become more stringent in future energy code updates.
California Title 24 2016 mandates plug load control in private and open office areas, reception lobbies, conference rooms, kitchens, and copy rooms. Controlled receptacles must include an auto-OFF control for when space is typically unoccupied, including an override control and holiday schedule control.
ASHRAE 90.1-2013 has expanded the role of automatic plug load control beyond private and open office areas to incorporate computer classrooms, conference rooms, print/copy rooms, break rooms, classrooms and individual workstations--including modular partition receptacles. Fifty percent of all receptacles must be controlled by an automatic control device that functions on an occupancy sensor, time schedule or a signal from another control or alarm system.