A preliminary engineering analysis of the potential for reducing peak electric demand by using indirect evaporative cooling in new small office buildings is presented. Peak reductions of 11 to 16% are shown, depending upon location in one of the 11 U.S. cities studied. The reductions are achieved by precooling ventilation air and exhausting energy from the lighting system to the ambient environment, resulting in reduced equipment sizes. The indirect evaporative cooler is assumed to be an integral part of a single-zone rooftop unit that is provided to cool a 10,000 ft2(929 m2) single-story office building. Cost comparisons between rooftop cooling systems that incorporate indirect evaporative cooling and conventional vapor-compression rooftop cooling systems show that peak electric power reductions in new single-story office buildings can be achieved at a fraction of the cost of providing the power in new electrical generating facilities.