Laboratory Plug Loads: The Final Frontier for Energy Efficiency

Eric Soladay, Rumsey Engineers

Architects and engineers usually implement energy efficiency strategies in three areas: building envelopes, HVAC, and lighting. Efficiency is not the architect's or engineer's traditional responsibility, but it is an important piece of whole system design; it is often based on plug loads, the energy used by the equipment and appliances in buildings. In two recent projects, Rumsey Engineers completed comprehensive studies of plug loads that show that significant energy can be saved in building equipment at relatively low cost.

In super low energy laboratories, when building loads have already been reduced significantly, plug loads can make up a proportionately larger percentage of the total energy use—up to 50 percent or more—so savings gained from reducing plug loads have a more significant effect on total energy use. Until now, no one has considered this approach to whole building design. Except for HVAC equipment, architects and engineers focus on the building only and not the equipment in it.

Plug load reductions present a hidden source for energy efficiency. In these projects, the team learned that once the client was motivated to analyze plug loads, getting equipment manufacturers on board with providing lower energy equipment was not as difficult as originally expected. And identifying a few surprising areas of wasted energy in otherwise highly efficiency-conscious user groups proved to be another important motivator. In other words, the barriers to reducing plug load energy use are primarily behavioral, not technical.

The long-term implications of addressing plug loads in critical facilities and other building types are significant: substantial reductions in energy use have been implemented in other products in the residential sector long ago, notably with refrigerators, air conditioners, and light bulbs. These reductions came about as a result of a combination of customer demand, government regulation, and the collective voluntary actions of equipment manufacturers. These plug load studies point toward an established protocol and methodology for measuring plug load energy use, which will help critical facilities to work with equipment manufacturers to develop more energy-efficient products.

This presentation will feature results from two recent projects, an office building and a laboratory, where plug load studies found an average of 50 percent energy savings. In carrying out these studies, a formalized methodology for examining laboratory plug loads was established. This involved surveying the current equipment and its use schedule; monitoring a selection of this equipment to formulate a baseline energy trend for plug loads; and undertaking extensive research and development to explore possible energy saving options.


Eric Soladay is an innovative, goal-oriented mechanical engineer responsible for the procurement, management, and design of building engineering system projects with architectural and social significance, sustainable and efficient systems, and cost- and maintenance-conscious designs. As project manager and mechanical engineer of record at Rumsey Engineers, Mr. Soladay has led several significant projects, including the ADC Green Datacenter, a 180,000-square-foot data center with groundbreaking energy-efficient design; University Plaza, a 190,000-square-foot mixed-used retail/commercial development in Palo Alto, California; and the 30,000-square-foot Packard Foundation Headquarters, a commercial/institutional zero energy building. Before coming to Rumsey Engineers, Mr. Soladay was a senior engineer at Gotama Building Engineers in Los Angeles, California, where his projects included laboratories and clean manufacturing facilities, hospitals, academic buildings, and central plant design for a wide range of clients including: Advanced Bionics, Scripps Health: Memorial La Jolla Hospital; Mercy Hospital; Glendale Memorial; City of Hope's Beckman Research Institute; West Los Angeles College; Hyperion Environmental Learning Center; Los Angeles Museum of Contemporary Art; and the Morongo Band of Mission Indians. Mr. Soladay is a LEED Accredited Professional and a Registered Engineer in California and Texas.

He received his Bachelor of Science degree with honors in mechanical engineering from the University of Texas at Austin. He is a board member of the Southern California ASHRAE Chapter.