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Project Launch: 01/01/2019

Partner: National Renewable Energy Laboratory

ComEd's research partnership with NREL examined the energy and peak demand savings potential of new rooftop unit (RTU) technologies.


This project was part of a four-stage effort by ComEd to evaluate the energy-savings potential of emerging technologies in the Chicago area. The first stage evaluated the potential for energy and peak demand savings of RTUs, including:

  • Two-stage RTUs
  • Variable-speed compressor RTUs
  • Switched reluctance motor (SRM) RTU supply fans


Simulation results revealed that upgrading an RTU with a variable-speed compressor and SRM supply fan can result in annual HVAC energy savings of 23–53%, depending on the application. Among building types, standalone retail buildings had the highest total energy savings (53%) while warehouses had the least (23%).

Compared to RTUs with two-stage compressors, variable-speed compressor RTUs delivered an average of 3.2% greater annual HVAC savings per building. Using SRMs boosted savings even higher, with an average of 7.7% compared to variable-speed units.

Download the full report from NREL's website, or email the Emerging Technologies Team to This email address is being protected from spambots. You need JavaScript enabled to view it..