Nearly a quarter of a buildings’ electricity use still occurs when no one is there.

The COVID-19 pandemic has profoundly altered our work patterns. Office vacancy rates in the United States recently surpassed 20 percent for the first time in decades. Even where offices are leased, they are underutilized. Attendance is significantly reduced and many buildings that were once bustling five days a week might now be largely empty much of the time. Yet, despite this reduced occupancy, the energy consumption in these buildings remains surprisingly high.

“Nearly a quarter of a buildings’ electricity use still occurs when no one is there,” said Sadia Gul, graduate researcher at the UC Davis Energy Graduate Group, whose research is looking into this issue of energy use in vacant buildings. “During nights, weekends, and holidays, when buildings are typically empty, they continue to guzzle electricity. The pandemic highlighted this issue when electricity use in many buildings remained high despite significantly reduced occupancy.”

Sadia Gul, Ph.D Student, UC Davis Energy Graduate Group

Sadia and her fellow researchers studied the energy consumption of UC Davis buildings when they were vacant and identified the culprit responsible for the energy consumption: Devices like security systems, network equipment, elevators, and more, collectively known as Miscellaneous Electrical Loads, or “MELs.”

“We found that MELs are responsible for much of the energy consumption during these periods,” said Gul. “Our goal is to develop a way to accurately determine when a building is vacant so that information can then be transmitted to MELs to optimize energy consumption.”

The researchers propose a novel approach to trim energy waste during vacant periods. By using sensors and data sources to estimate the likelihood of a building being vacant – known collectively as a “vacancy inference engine” – the MELs can enter a “vacancy mode” that significantly reduces their power consumption.

Several types of MELs were identified as potential candidates for this vacancy mode, including hot water recirculation pumps, Wi-Fi routers, restroom ventilation fans, and more. The researchers estimated that this strategy could lead to energy savings of up to 95% for participating MELs during vacant periods, contributing to a substantial reduction in overall energy consumption.

“The research provides a promising approach to address the energy inefficiency associated with unoccupied buildings,” says Gul. “By developing innovative strategies to optimize energy use during vacant periods, we can make significant strides toward a more sustainable and efficient future of building operations.”

To learn more about the UC Davis Energy Graduate Group, visit here.