Research Publications

A life cycle optimization of the replacement of residential central air conditioners (CACs) was conducted in order to identify replacement schedules that minimized three separate objectives: life cycle energy consumption, greenhouse (GHG) emissions, and consumer cost. The analysis was conducted for the time period of 1985-2025 for Ann Arbor, MI and San Antonio, TX. Using annual sales-weighted efficiencies of residential central air conditioning equipment, the tradeoff between potential operational savings and the burdens associated with replacing with new, more efficient equipment was evaluated to minimize the objective. The optimal replacement schedule for each objective was identified for each location and service scenario. In general, minimizing energy consumption required frequent replacement (4-12 replacements), minimizing GHG required fewer replacements (2-5 replacements), and minimizing cost required the fewest replacements (1-3 replacements) over the time horizon. Scenario analysis of different federal efficiency standards, regional standards, and Energy Star purchases were conducted to quantify each policy’s impact. The results of the analysis support the establishment of regional efficiency standards to cost effectively reduce energy consumption and GHG emissions. The results also show that proper servicing should be a higher priority than optimal replacement to minimize environmental burdens.