Drop and give the planet 20 (degrees, that is)

Turn down your water heater thermostat. Thermostats are often set to 140 degrees F when 120 is usually more than adequate.  

Each 10 degree reduction saves 600 pounds of CO2 per year for an electric water heater, or 440 pounds for a gas heater. If every household turned its water heater thermostat down 20 degrees, we could prevent more than 45 million tons of annual CO2 emissions – the same amount emitted by the entire nations of Kuwait or Libya. 

Another action you can take is to add insulation to the outside of your water heater. The greater the difference between the temperature of the water in your tank and that air in the room, the faster your water heater loses heat to the air. Extra insulation can slow down that heat loss. 

To see heat loss in action, take two ice cube trays.  Fill one with very hot water and the other with cold water.  Note that they first start forming ice at the same time (or very close).  The hot tray must have lost heat faster than the cold tray in order to begin ice formation at the same time.