Americans wash 35 billion loads of laundry each year and heating water for the washing machine accounts for 90 per cent of the energy consumption and costs associated with this task. Washing clothes in cold water has been identified as a way to increase energy efficiency and lower utility costs. However, the use of cold water to kill germs is highly controversial. Scholars argue that using cold water in a washing machine does not kill germs and can actually spread them while others promote this practice as an effective, economical part of sustainability.
According to the University of Kentucky's College of Agriculture, laundering clothes in cold water is not effective in killing germs. New Mexico State University's College of Agricultural, Consumer and Environmental Sciences agrees and says that neither cold nor warm water will kill germs. However, Beaches Energy, which provides electrical energy to the Jacksonville, Florida area disagrees, stating the following: "You don't have to wash clothes in hot water to kill germs." Beaches Energy also states that cold water combined with washing powder is effective in killing germs, and those who use hot water are wasting energy and money.
To effectively kill germs, the University of Kentucky advises users to set their washing machines to the hottest setting and use the longest agitation cycle possible without damaging clothing. New Mexico State University concurs that hot water seems to be more effective in eliminating germs. However, Beaches Energy argues that the temperature of hot water is not high enough to kill any more germs than cold water and since most detergents are designed for cold water use, hot water is an unnecessary expense.
New Mexico State University asserts that when a disinfectant (not to be confused with detergent) is used in cold or warm water, it will destroy germs. Dr. Kelly Reynolds at the University of Arizona agrees and notes that some viruses can survive in any washing machine temperature and recommends using bleach or some other disinfectant to destroy them since water heaters in the U.S. are generally not set at the temperature required to kill germs. And since bacteria can survive detergents, Reynolds says that washing machines are actually contaminated and can spread bacteria from one load of laundry to the next.
Charles Gerba, in "Applied and Environmental Microbiology," writes that apart from disinfectants, the clothes dryer presents the most effective means of destroying germs. The University of Kentucky advocates killing bacteria by either drying clothes outside on a clothesline on a sunny day or in the clothes dryer. The sun's ultraviolet rays are a successful way of destroying germs, but the dryer is even more effective when using the hottest temperature and the longest cycle. Ironing and steam pressing are also recommended as effective germ-removal strategies.