Since shower water is a mixture of hot and cold, tank size, tank temperature, and cold water temperature are the predominant factors, at least initially.
For a given shower temperature, hot water consumption rate will increase at an exponential rate until tank temperature falls to shower temperature, then shower temperature will fall.
It’s not the size of the water heater, it’s the volume of water output.
Since shower water is a mixture of hot and cold, tank size, tank temperature, and cold water temperature are the predominant factors, at least initially.
For a given shower temperature, hot water consumption rate will increase at an exponential rate until tank temperature falls to shower temperature, then shower temperature will fall.
We were making sexual innuendos, not having a real conversation on water heater capabilities.
Anyway instantaneous (in-line) heaters exist, I’ve got a 35-year old one, never runs out of water, it doesn’t have a tank.