Looking Through the Duct at Plug Load Reductions

Alison Farmer, kW Engineering

After years of neglect, lab plug load energy efficiency is receiving well-deserved attention. However, savings claims for plug load reduction projects are incomplete without an analysis of the associated HVAC systems' response to the changes. Because of the high ventilation rates used in labs, the impact of load changes on HVAC energy usage often differs from that observed in other building types. Plug load reductions can be significantly amplified by HVAC system savings, or in the worst case can be entirely nullified by a corresponding increase in electric resistance reheat. With an initial focus on ultra-low temperature freezers (ULTs) in California, we will describe the results of research to quantify the state-wide magnitude of these "indirect" energy savings by exploring the demographics of the HVAC environments of ULTs. We will demonstrate how to identify plug load efficiency projects to maximize energy savings, and will discuss the how these conclusions are affected by the latest trends in lab efficiency retrofits and new building designs.

Learning Objectives

  • Rank lab building energy end uses (including plug loads and HVAC systems) in order of typical annual energy consumption
  • Discuss the ways in which different HVAC system types respond to plug load reductions
  • Describe the demographics of lab building HVAC systems in California
  • Identify the most promising targets for plug load efficiency projects


Alison Farmer is a physicist with a deep dedication to energy efficiency in buildings. Ms. Farmer has extensive experience as an energy efficiency consultant for lab facilities, from strategic planning to detailed energy savings calculations. She has taught classes on energy analysis and is chair of the I2SL Lab Benchmarking Working Group. Ms. Farmer holds bachelors and masters degrees in physics from the University of Cambridge and a PhD in astrophysics from Caltech.


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