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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 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
  • Smart switched-reluctance motors


Simulation results revealed that upgrading an RTU with a variable-speed compressor and SRM supply fan can result in annual energy savings of 3–23 percent. Among building types, standalone retail buildings had the highest total energy savings (23 percent) while warehouses had the least (3 percent).

Compared to RTUs with two-stage compressors, variable-speed compressor RTUs delivered an average of 1.5 percent greater total energy savings per building. Using SRMs boosted savings even higher, with an average of 2.5 percent compared to variable-speed units.

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