It's a common misconception that washing your hands in hot water kills bacteria. While it's true that high temperatures can be effective at eliminating bacteria, the temperature required is much too hot for human skin, according to a study by the Vanderbilt Institute for Energy and Environment.
The average person who uses hot water to wash his or her hands typically uses water that's 104 to 131 degrees Fahrenheit. But the temperature needed to effectively kill bacteria is much hotter. For example, to disinfect drinking water, experts recommend boiling the water at 212 degrees. Temperatures that high could not only scald your hands but irritate them so much that the skin becomes less resistant to bacteria.
Instead, the study found that washing hands in cold water, as chilly as 40 degrees, can be just as effective at reducing bacteria as hotter water. You just have to make sure you properly scrub your hands with soap, rinse well and dry thoroughly.
According to the U.S. Department of Energy, the hot water heater is the second largest energy expense in your home, costing the average household $400 to $600 per year. Eliminating hot water waste from hand washes could help you save money and energy each month.
Americans collectively wash their hands approximately 800 billion times each year. If hot water was replaced with cold water for each time, it would save more than 6 million metric tons of carbon dioxide emissions. According to National Geographic, that's equal to the emissions from 1,240,000 vehicles in a year, 299,700 homes or two coal-fired power plants. It even points out that the energy saved would be more than the emissions output from Armenia or El Salvador.
More tips to minimize hot water waste
- Turn your water heater down. Most hot water heaters are preset to 140 degrees, which is actually much hotter than most homes need. Turn back your water heater to 120 degrees and you could save 3 to 5 percent on your water heating costs, according to the American Council for an Energy-Efficient Economy.
- Install a low-flow showerhead. Hot water may not kill bacteria, but that doesn't mean you need to take cold showers from now on. However, you can make your showers more efficient if you install a low-flow showerhead that uses less water. According the DOE, low-flow fixtures can achieve water savings of 25 to 60 percent.
- Wash your clothes in cold water. ENERGY STAR says about 90 percent of the cost to operate your washing machine comes from heating water. Whenever possible, wash your clothes in cold water to save energy. If you don't want to use cold water, warm is still a better option than hot because it requires half as much water heating.