Most water heaters are factory set to 140 degrees, but you could reduce that to 120 degrees and not feel any difference in your shower.
Lowering the temperatures by 20 degrees could mean a savings of at least 6 percent in your water heating costs.
Think about getting a low-flow shower head, which uses at least 25 percent less water. Many of these shower heads costs less than $20, and you won't feel a difference in the water pressure.
If you have an older water heater that lacks built-in insulation, consider buying a jacket or blanket for the heater, especially if it's located in a cold area. Such jackets cost between $10 and $20, but they could save you an added 4 to 9 percent on water heating costs, adding that the cover would pay for itself in about a year. You can get a jacket or blanket at any hardware store.