I am the first person to shower five days a week at 5am. During the winter, the hot water runs out shortly into my shower, even if I run only a little water. It also happens on the rare mornings when I shower at 3:30am.
This does not happen to any other family member’s shower later in the day or when I am the first one to shower later in the morning on my day off.
The hot water heater is four years old. We’ve had two service representatives here who cannot find a heating problem with the tank. One suggested raising the water temperature, but it didn’t solve the problem.
My first thought is to tell you not to get up so early.
Your heater has a defective gas control valve. The valve does not sense the gradual cooling of the tank over the night hours. Once the first morning shower (yours) drastically lowers the water temperature in the tank, the valve kicks in and raises the tank water temperature to normal levels.
A new gas control valve should solve the problem. Keep in mind, however, that “winter water” entering your plumbing system is considerably colder than summer water. Thus, any water heater will need to work harder during the cold months.