Optimal Clothes Washer Replacement Policy for Households
The energy efficiency of the average clothes washer in the U.S. improved by 88.4% from 1981 to 2003. Replacement of old vertical-axis washers with new horizontal-axis washers results in decreased operating costs, both environmental and economic. But replacement also results in one-time financial and environmental impacts from purchasing, manufacturing and disposition. A Life- Cycle Optimization (LCO) model developed to quantify this tradeoff and determine optimal replacement intervals for residential clothes washers. Life-Cycle Inventory (LCI) and Life-Cycle Cost (LCC) profiles were defined for each model year clothes washer from 1985-2020. These profiles represent four life-cycle phases of a washer. In addition to characterizing the material production, manufacturing and assembly, use, and end-of life management phases of the washer, the optimization model also includes key parameters that represent water heating and clothes drying. Decisions for washer replacement are dependant on the technology and equipment age of a household’s water heater and clothes dryer. These two system components expand the boundaries and complexity of the optimization. The results of the LCI and LCC studies showed that the use phase of the washer’s life cycle accounts for 96-99% of energy, carbon dioxide emissions and water use, but just 61%-86% of total costs over an anticipated 20 year life. From an energy or carbon dioxide emissions perspective, any average washer, regardless of model year, should be replaced with a new horizontal-axis washer in 2006, 2011 and 2016. In addition to a base case that seeks to model the typical American household, four alternative scenarios were examined. Alternative simulations were run with electric water heater instead of gas, cold water washing, line drying, and different energy price forecasts. The replacement patterns for washers will be contrasted with other product systems including refrigerators and automobiles to draw general conclusions about optimal product replacement from environmental and economic perspectives.