When selecting equipment for a building, it is important to consider the energy use of the product during use and, if applicable, in standby mode. Any device plugged in may have hidden phantom loads, which continue to draw power even in a turned-off state, and can constitute about one third of the active energy use.4 Rating systems, such as Energy Star in the United States, can make it easier to identify efficient products.
In buildings that have photovoltaic or other onsite energy generation, DC microgrids can provide greater energy supply efficiency. Onsite energy is produced in direct current (DC) and converted to alternating current (AC) for distribution throughout the building. However, devices such as personal computers, laptops and desk lamps convert the power back to DC for use. DC microgrids can bypass multiple energy conversions and save between 10% and 40%.5
Occupant behavior can have a large impact on plug loads, but is also very difficult to control. Providing occupants with feedback is one of the most effective ways to increase awareness and change behaviors. Detailed monitoring through publically visible dashboard systems can show real-time energy use. In office settings, individual workspaces can be monitored and monthly feedback can be given on paycheck, as email alerts, or simply as friendly competition. Signage and other reminders can raise employee awareness about turning off equipment and conserving energy.
Although changing occupant behavior is vital, the most effective way to immediately reduce plug load usage is through control systems with automatic shut-offs.6 There are a variety of occupancy-sensor based automatic shut offs that can help to prevent unnecessary plug loads and phantom loads. Power strips, wall outlets, and circuits with occupancy sensors can all be used to shut down equipment in unused spaces. There is also equipment that can be installed to shutdown circuits when a security system is activated.
Also, power sensing plug strips will turn off all outlets on the strip once the power on one of the devices decreases. For example, if a computer is plugged into the master outlet, when the computer is turned off or goes to sleep, the printer, speakers and other devices plugged into the power strip would be automatically shut off.
Perhaps the simplest form of reducing plug loads however, is through an automatic timed shut-off system that can be set to turn devices off after a period of time without use, at night or after the hours of operation.