It is refreshing to take a cool shower in hot weather. And for the sake of discussion, lets assume that one should be "comfortable" with temeratures when taking a shower.
Considering that the vast majority of the heat from a shower is lost down the drain, would it not be more energy efficient to heat a confined space (shower stall) to a temperature that would allow you to shower with cool water rather than hot?
How hot would it have to be in the room for 70 degree water to be "nice." 60 degree?
And since all of the energy used to heat the air in the space would remain in the space/room, would you use less energy to take a comfortable shower doing it that way?