Ranty has some great energy saving tips on her Healy House blog, including one regarding home’s hot water temperature:
8. Stay out of hot water. Water heating accounts for 15 percent of household energy use. Reduce water heating costs by lowering the water heater’s thermostat setting. Each 10ºF reduction can save between 3-5 percent in energy costs. Also insulate the hot water heater and hot water pipes.
Good point. Adjusting it is really quite easy, saves money, and makes your hot tap water more usable.
Pick up a food thermometer (I use the one on the right) and stick it under a running stream of hot water from your tap.
You definitely don’t want it scaldingly hot, which is ~150F. The government suggests that 120F is a temperature that is hot enough to clean clothes and dishes without scalding skin. Natural Handyman explains that you may need to consider 140F if your dishwasher doesn’t include a heater.
To adjust the heat, make slight turns to the dial near the bottom of the hot water heater, wait a few hours, then re-test.