Rain shower heads do use a bit more water than a normal shower head does or a lower flow shower head.
However rain shower heads made today don't use as much water as they used to use before.
Most rain shower heads will use around 2.5 gallons of water per minute.
I love my rain shower head as it gives me a much better and more enjoyable shower and cleans me off better than a normal shower head.
If you take a 10 minute shower then you would use a little over 20 gallons of water in the 10 minute shower using a rain shower head.
That's not all that much water.