lower the temperature on your water heater.

You can reduce your water heating costs by simply lowering the thermostat setting on your water heater. For each 10ºF reduction in water temperature, you can save between 3%–5% in energy costs.
 
Although some manufacturers set water heater thermostats at 140ºF, most households usually only require them set at 120ºF or even 115ºF. This is hot enough to prevent bacteria build up but not unnecessarily hot.
 
Reducing your water temperature to 120ºF also slows mineral buildup and corrosion in your water heater and pipes. This helps your water heater last longer and operate at its maximum efficiency.
 
Potential annual savings: $450 and 215 lbs. emissions.