Water heaters of the same size can heat water at different rates, depending on the burner's fuel source (gas or electric). The size of the burner at the base of the heater also affects the speed of the tank.
Water heaters can range in size from 20 to 120 gallons, with most tanks being somewhere in the middle. Gas tanks heat water faster than electric tanks, and larger burners heat faster than smaller burners. Larger families and larger houses will need a higher-capacity tank.
The average 50-gallon gas heater should take between 30 and 40 minutes to heat up water. Most electric heaters will heat 20 to 25 gallons every hour. Gas heaters heat water faster.
You can always turn up the temperature on your water heater. This will help the water heat up faster. Turning the water tank to a higher temperature also allows you to use less hot water when you are trying to produce lukewarm water to bathe, shower or wash dishes. This is because it requires less hot water to mix with the cold water to make lukewarm water.
Use caution when turning the temperature higher, and do not raise it past 48.9 degrees Celsius. The danger of getting burnt increases with higher water temperature.