Unilever have recently carried out a study investigating how much time people spend in the shower and how they use other Unilever products. This found that the average shower lasts 8 minutes, so the average shower uses almost the same amount of water as having the average bath. The numbers get worse if you have a power shower, as this uses much more water per minute, so an 8 minute power shower will use more water than a bath.
HildeHendrickx, from Unilever explained that
quite a large proportion of our (products') environmental impact occurred when people used them
and, in particular for shower and bath products,
we know that 95% of the associated greenhouse gas emissions are related to people [using] our products because they have to use hot water.
So, if you carefully use every last drop of shampoo and then recycle the plastic bottle this isn't doing as much green good as if you cut your shower by a few minutes. I was really surprised at the 95% figure, I would probably have guessed maybe 50% of a bottle of shampoo's carbon footprint was from using hot water with it, so it shows how important good research is.
Today from my alarm going off to being back in my room having had a shower it took me 8 minutes, so I think my shower was probably 5 minutes long. I know I take much shorter showers than a lot of my friends so if we all cut a minute or two off our showers hopefully we'll have a greener world.