If a building’s occupancy drops by 50-80%, by how much should its energy use go down? Unfortunately, there is no easy answer to that question – it depends on many factors, some of them commercial, some highly technical. And, as many of the amazing facilities and engineering managers we work with are demonstrating to us on a daily basis, there is rarely a fixed answer.

Across the globe, people are being encouraged to stay at home to avoid spreading the COVID-19 virus. Buildings with fewer people in them have less work to do, obviously, but they still need to provide services. Health and safety standards need to be met and comfortable conditions need to be provided for those who cannot stay at home. But equally, it has never been more important to save energy and, in times like these, no business can afford to waste cash.

Our team has been working closely with building operators across the globe to trim and tune their building systems to match occupancy requirements. Unfortunately, not everyone has been in a position to make sophisticated changes just yet; however, on the plus side this has given us the opportunity to evaluate the effectiveness of those strategies that have been deployed (in statistical terms these BAU operators can be called a “control group”).

The following graph shows the savings path of 176 Australian commercial office buildings where occupancy has dropped by more than 50% since mid-March 2020 when physical distancing restrictions started coming into effect. The red line indicates electricity performance for 126 buildings that have had vacant floors switched off but no targeted energy saving initiatives have been implement (i.e. they’ve done the minimum, not nothing). The blue line indicates the savings achieved at 50 buildings where some or all of the energy savings initiatives listed below were implemented.

Energy consumption for buildings that implemented energy saving initiatives vs. buildings that did not implement savings initiatives

We found that in buildings where the managers actively implemented energy saving initiatives, usage dropped by an additional 12% compared to those where only the air-conditioning was shut off to vacant floors. Importantly, as illustrated in the following chart, the gap is widening by the day as initiatives are implemented, reviewed and further refined.

Results from implemented energy-saving initiatives

What did they do? All commercial buildings are unique, of course, and different energy saving initiatives will have varying degrees of success depending on the situation. Nonetheless, here is a list of strategies that appear to be delivering consistent savings across multiple buildings:

  • Widening zone temperature control dead-bands
  • Increasing chilled water temperature setpoints
  • Optimizing chiller and compressor staging
  • Increasing chiller lockout temperatures
  • Turning off unnecessary screens, lighting, and vertical transportation
  • Trimming start and stop times
  • Increasing minimum supply air temperature setpoints
  • Temporarily closing end of trip facilities.

Most people assume that a building’s energy use will drop roughly in proportion to a reduction in occupancy. If only it were that easy! So far, our analysis suggests that without highly engaged and active management, energy savings will only amount to about half of the occupancy reduction. I.e. a 70% reduction in the number of people in a building might lead to a ~35% reduction in energy use. Or phrased another way: as buildings are vacated for COVID-19, their energy efficiency typically halves. Fortunately, our analysis also shows that this need not be the case. Active and effective building management is as valuable as ever, probably even more so.