You Use Less Energy Taking a Shower Than a Bath.
This is sometimes a myth, but it is sometimes true. It depends on your shower head and whether it has a flow restrictor in it and how long you shower.
If your home was built before 1992, chances are your showerheads put out about five gallons of water per minute (gpm). Multiply this by the number of minutes you're in the shower, and the water adds up fast!
An average bath requires 30-50 gallons of water. The average shower of four minutes with an old shower head uses 20 gallons of water. With a low-flow shower head, only 10 gallons of water is used.
To test the amount of water used in a shower vs. a bath is to put the plug in the bath next time you take a shower (but not a stand-alone shower as you might spill over the lower shower wall).
After you've showered, see how much the tub filled up.
If there is less water than you would usually have in a bath, then you will probably save money by taking a shower instead of a bath.