Showering in the morning can be a gamble in some apartments and households. If you're the first one up, you're fine, but if not, you may have a cold morning.
The Science Channel looked into how hotels keep enough hot water on hand for all of the guests. They don't store it in a tank like in most American homes, instead they heat the water and constantly pump it throughout the building, ensuring everyone uses it at the same time. The process is intricate and complex, but without it we would all be out in the cold on our next vacation.
via Science Channel