Reducing hot water use saves energy because your hot water heater has less work to do. Recent research has shown that on average about 73% of the water used in a typical shower is hot water (DeOreo, et. al. 2001).
Photo source: Aquacraft, Inc., by permission.
Installing a new showerhead is a good idea and can result in some energy savings, particularly if you live in an older house and have what appears to be an older showerhead. Showerheads are inexpensive (starting at less than $5) and can be a good way to save money in your home.
If you are looking for further energy savings in the shower, consider taking shorter showers. If your showerhead uses 2.5 gpm, then you can save about 1.8 gallons of hot water for every minute you reduce your showering.