How do you get more quantity hot water from your hot water heater?

Answer 1

Install a bigger water heater. This would only be efficient if you had a constant need for an increased volume and could bear the added cost of installing, operating and maintaining a larger heater.

Or increase the temperature on the water heater so you use less to get warm water. This also has its practical limits, where water could be delivered to the faucet at a dangerous temperature (over 130 F), unless properly controlled.

Or install another water heater in parallel, giving you twice as much hot water before it starts getting cool. Larger facilities may have three or more heaters in parallel and another one in series for pre-heating the supply to the others.