Question: how long does it take for a 50 gallon water heater to fill up?
Answer: A 50-gallon hot water heater with 5,500-watt elements set to 120 degrees takes about 1 hour and 20 minutes to heat water coming in to the unit at 60 degrees. Conversely, when the water entering this same tank is 40 degrees, it takes 1 hours, 47 minutes to heat it up.