The water heater is a large tank that normally heats up the water to temperatures. As we use the heated water stored in the tank, cold water enters the tank to replace it and is then heated. The thermostat detects the drop in temperature and turns on the elements to begin heating up the cold water. Electric water heaters have two elements, an upper and a lower one.
Make sure the replacement thermostat is the same model, size and rating as the one you are removing. It's very easy to replace by just unscrewing the old one from the mounting and screwing the new one in. You will want to check the owner's manual again to adjust the thermostat. Once you have it adjusted, place the access panels back on and turn the breaker on. You will soon have hot water.
Will Plumbing and Heating technicians are equipped to work on heating and air conditioning equipment.