Life Cycle Optimization of Household Refrigerator-Freezer Replacement
Average energy consumption of new refrigerators sold in the U.S. decreased by approximately 60 percent between 1980 and 2002. Despite the dramatic energy efficiency improvements driven by energy standards, the average replacement intervals of refrigerator remain nearly unchanged being around 14 years. Although replacing old refrigerators with new, more efficient units is an important strategy, it also leads to environmental impacts in producing new refrigerators and disposing old units.Using a Life Cycle Assessment perspective, this research examines optimal refrigerator lifetimes that minimize cumulative energy consumption and cost over the time horizon between 1985 and 2020. Dynamic life cycle energy inventories for mid-sized top/bottom refrigerators were developed for model years between 1985 and 2020 based on available data. Parameters such as energy efficiency improvement and energy performance deterioration were also modeled. Additionally, life cycle costs for purchasing, operating, and disposing a refrigerator were estimated.
The Life Cycle Optimization (LCO) model for refrigerator replacement was developed based on a dynamic programming tool. According to the simulation results based on refrigerator energy consumption data from Consumer Reports, the optimal lifetime for the energy objective ranges between 2 to 12 years, while that determined by cost objective is 18 years over the time horizon between 1985 and 2020. The results show that energy optimization scenarios would save 17 to 21% of primary energy use compared with cost optimization scenarios, but require 22 to 33% higher cost than cost optimization scenarios.
The results can help manufacturers, consumers, and policymakers understand the economic and environmental implications of retiring old refrigerators and purchasing new units. The results also demonstrate that scrappage programs encouraging retirement of old, inefficient refrigerators can serve to reduce household energy consumption.