How long does it take a water heater to heat up?

 How long does it take a water heater to heat up is the question of every water heater owner? Every owner needs the minimum time to heat the water. Here we talk about the time taken by the gas and electric water heater. This is universal truth if the inlet water temperature is low, then a water heater of every kind takes a long time to heat up.

Overall the gas tankless water heater is more efficient than the electric tankless water heater. It does not mean that an electric tankless water heater is not good. But in some places, electric tankless water is more efficient than the gas tankless water heater.

Some averages of electric and gas tankless water heaters:

 Of course, this is only a rough estimate that the water heater will vary depending on age and model.

  • 40-gallon gas water heater: 30-40 minutes
  • 50-gallon gas water heater: 40-50 minutes
  • 80-gallon gas water heater: 60-70 minutes

You’ll have hot water after a little longer if you have a 5000-watt electric tankless water heater set to 100 degrees, and the incoming water temperature is around 50 degrees. Units of 50 to 60 gallons will take one hour and forty minutes to complete.

6 Factors That Affect the Heat Time

Generally, many factors affect the heat time of the water heater. But we will discuss the most common factors that affect heat time.

First-Hour Delivery Rate (FHD)

In the realm of water heaters, FHD stands for first-hour delivery, and rates are expressed in gallons per hour. The first-hour delivery rate applies to all water heaters. When the heater is full of water, the FHD tells how many gallons of hot water it can provide in an hour.

Water Heater Recovery Rate:

The high recovery rate of a unit will immediately provide hot water. If you’re using a massive amount of hot water simultaneously, a water heater with a high recovery rate will be able to heat the incoming cold water swiftly.


Distance from the water heater to the shower also affects the heat time. Because in cold weather, if the outside temperature is less than hot water travel from the pipe. Then water inside the pipeline becomes cold. This is the reason that affects the heat time.

Power source: 

A Gas and Electric tankless water heater’s power source has a lot to do with how long it takes to heat water. For heating purposes, the gas tankless water heater takes little time to heat the water. This is because electrical heating elements are less efficient than gas.

The average 50-gallon gas and electric water heater might have an FHD rate of 80 to 90 GPH and 60 to 70 GPH, respectively. 

Water Heater sort

Water heaters that store and heat water are known as storage water heaters.  Tankless water heaters do not have storage tanks and heat the water as it is being dispensed. The time it takes these two types to heat water differs dramatically. To heat up, it takes 20 minutes to an hour for a storage water heater.  In most cases, a tankless water heater provides instantaneous hot water. The flow rate will slow down if too much hot water is used at once, but the water that comes out will still be hot.

Water Heater Size: 

Smaller tanks heat water faster. This is because the water in the small tank will boil more quickly. But water heaters do not take a long time to heat up. Again, this is because bigger electric models have two heating elements to help the process along.

A large gas burner is used in large-capacity gas water heaters to help them heat up faster. For example, if you have a 30-gallon water heater, you won’t have to wait as long for it to heat up as you would with a 50 or 80-gallon unit. 

Unusual Water Temperature: 

The water temperature has a significant impact on how long it takes for a unit to heat it. If the water temperature of inlet water is low, the water heater will have to work harder to get the water up to the desired temperature. The input water temperature in cooler climates usually is around 40 degrees Fahrenheit. It’s approximately 50 degrees in warmer climates. Therefore, the water heater takes time to heat water.

Plumbing Issues & Solutions: 

Also, there are plumbing issues that affect the heat time of the water heater. Why water heater takes so long for them to get hot water is not a long run. It’s known, it’s maybe 25 to 40 feet somewhere in that range to get to the kitchen healthy here’s the issue the house is plumbed in 1-inch plumbing all the outlets for the water all of the faucets the showers everything is a low flow it’s a restricted flow system which is supposed to save water now when you turn on a tap you know say 30 feet away from this point. 

It’s plumbed in one inch, and it’s one of those highly restrictive faucets. All the water in this one-inch pipe has to be replaced. Because this water’s been sitting here overnight, and now it’s fantastic. You have to replace all the water inside this one inch, and that will take up to 10 minutes when it’s a highly restricted faucet, which happens to be in this house. Therefore, it takes a very long time to replace the cold water inside that pipe with hot water. 

The customer would have been much better served in this particular home if they’d plumbed the hot water in a half-inch, maybe 3/4, but 1/2 inch would have been much better because it would have taken about one-sixth the amount of time to get hot water to the places where you need all right, so that’s what’s going on here. Bigger is not always better, and in this case, it is worse, so you messed up by putting one inch for the outlet line for the hot water. Unfortunately, the house has a finished basement, and it’s going to be very difficult to replumb this at this point.


Through research, it is proved that electric tankless water heaters took a long time to heat up. But in some places, these heaters are more efficient than other water heaters. It depends on the situation and areas. The answer to this question of how long it takes to heat up depends on the pipes, conditions, fitting, brands, power type, inlet water temperature, distance, and other factors.

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