Your household water temperature should be between 120-130ºF if your dishwasher has a heat booster (or you don't have a dishwasher) and if your dishwasher does not have a heat booster, then the water temperature should be between 130-140ºF. With each 10ºF reduction in water temperature, you can save between 3%-5% in energy costs, so now is a good time to check the temperature on your electric water heater.
Before you make an adjustment to the water heater, check the temperature of the hot water as it comes out of a faucet closest to the water heater. Place a glass under the stream and insert a cooking thermometer. After three minutes of letting the hot water run, if the temperature is less than 120ºF or higher than a temperature needed to sanitize dishes, you need to adjust the water heater's temperature gauge.
An electric water heater has two heating coils, one each at top and bottom, and each needs to be adjusted to the same temperature.
Locate the two covers on the front of your water heater. The covers will be almost identical in size and rectangular in shape. The covers are held on with screws. Remove the screws from both covers. If your water heater has been insulated, you will need to pull back the insulation to get to the covers.
Most likely, the gauge will not have numbers but instead, the gauge will have hash marks or letters. Twist the gauge one hash mark up or down, to raise or lower the water temperature.
Because the water temperature doesn't instantly change, you will need to wait three hours, and then test the temperature again as depicted in Step 1. Repeat adjusting the temperature gauge until you get the desired temperature.