See our scientific paper:
and our blog:
The Shower Calendar consists of a display in the shower. Upon pressing a button, a large dot appears at the current date in a calendar-like matrix. The dot represents 60 litres of water (estimated consumption of 20-40 litres for showering per day and person in Germany). We added 30 litres to the average in order to allow extreme situations. When using water the dot gets smaller until the user either stops the water or the full amount of 60 litres has been spent. In the latter case, the dot is very small, but still a visible record. The concept is designed in a way that beautifies reduced consumption of water.