• Retrofitting packaged HVAC units with a modified (less aggressive) energy efficient controls package option (integrated differential dry-bulb economizer, multi-speed supply fan, single-stage capacity control and DCV) relative to modified base case with integrated differential dry-bulb economizer, constant speed supply fan and single-stage capacity control, results in average HVAC energy savings of about 28 percent for the small office building, 32 percent for the stand-alone retail and strip mall buildings, and 24 percent for the supermarket.

• For the modified packaged control option, average HVAC energy cost savings are 38 percent for all four building types.

• The maximum controller cost that will provide payback periods of no more than three years for all U.S. locations under current utility rates are $2,103 per controller for stand-alone retail, strip mall, and supermarket buildings and between $540 and $1,350 for small office buildings. The precise value depends on the number of square feet of floor space per controller (1,100 and 2,750 square feet, respectively, for the small office building costs given).

• Individual control strategies have different degrees of impact on energy and cost savings. The simulation results indicate that multi-speed fan control and DCV are the two control strategies contributing most of the savings. In many cases, multi-speed fan control dominates the impact in hot and mild climates (e.g., Miami and Los Angeles), while DCV dominates the impact in climates with significant heating and cooling loads (e.g., Baltimore) and cold climates (e.g., Seattle, Chicago, and Duluth).

PNNL noted that even if one-half of packaged HVAC units are retrofitted with the modified control package option, it will result in annual savings of approximately 55 trillion Btu (assuming the percent savings are 30 percent).

Publication date: 04/30/2012