Adjusting a water heater thermostat is a little harder than adjusting the thermostat on your furnace. This thermostat is meant to be set once and left alone, usually, the factory settings are suitable.
Not sure if this is your problem? See the article 'Troubleshooting Electric Water Heaters' for a complete listing of all of the problems related to an electric water heater.
Too Little Hot Water
Are you thinking of raising the temperature because you don't have enough hot water? Raising the temperature is not the way to solve this problem.
It is likely that you have another issue. The thermostats themselves may be malfunctioning or you could have a burned out heating element. See the articles 'Testing Electric Water Heater Thermostats' and 'Testing Electric Water Heater Elements' for information on checking to see if these items are functioning properly.
For safety reasons the water temperature adjustments for your electric hot water tank are hidden under a couple of layers. Make sure you follow the 'turning off the power' guidelines for electric water heaters. You will be very near some wires that have serious current in them when you make this adjustment.
There is a danger in setting the temperature too high. Water that is set to 160 degrees will give you a lot of hot water. It can also cause a serious burn in less than a second. Especially when there are children in the home should temperatures be set conservatively. Most manufacturers recommend a temperature setting of 120 degrees. Your water heater is likely set by the factory to that temperature.
See the article on 'Hot Water Heater Temperature Settings' for information on the correct settings and why setting it too high can be dangerous. Do you really want to change it?
WARNING!! Hot Water Can Cause Serious Burns!!! DO NOT SET YOUR HOT WATER TEMPERATURE TOO HIGH!!! WARNING!!!
Shutting Down the Water Heater
You need to shut down the power to the water heater before you attempt to access the thermostats. See the article 'Shutting Down an Electric Water Heater' for more information. Pay particular attention to the segment on shutting off the power.
Double check and make sure the power is off at the heater and make sure you tag the breaker.
Locating the Thermostats
Most water heaters have two thermostats. The are attached to the side of the tank. The locations of the thermostats are beside two removable plates on the side of the water heater.
You have to remove the metal covers on the outside of the hot water tank first. Then you will find some insulation that has to be removed or pushed aside to expose the thermostats and elements. Most models have a plastic cover that serves as an additional protection. You will need to remove the plastic cover to make the adjustment.
Adjusting The Thermostat
There is a screw that the can be adjusted with a flat blade screwdriver. The heat descriptions may vary. It may have the actual temperatures. Some of them have letter designations (A, B, C), while others may have the words 'Warm' or 'Hot'.
It is not common to need to adjust the temperature on your electric water heater. The factory settings are adequate in most situations. If you are not getting enough hot water, raising the temperature is not the solution. You likely have another problem such as a 'burned out element' or a 'faulty thermostat'.