If you have a storage water heater (one with a tank), it takes a little time for the water in the tank to get hot. But how long does it take for a water heater to heat up?
You need to know this whether you’ve just had a new water heater installed or just want to find out if your water heater is performing as it should.
In general, you can expect hot water within 30 minutes (gas) to about an hour and 20 minutes (electric) after filling the tank.
How Long Does It Take a Gas Water Heater to Heat Up?
A gas water heater is more efficient and heats water faster than an electric model. They burn natural gas as fuel and heat water in the tank with powerful burners on the bottom of the tank.
How fast a gas water heater can heat up depends on the temperature it’s set to and the temperature of the cold water it has to heat. Here are some averages:
- 40-gallon gas water heater: 30-40 minutes
- 50-gallon gas water heater: 40-50 minutes
- 80-gallon gas water heater: 60-70 minutes
The average gas water heater is around 40 gallons and takes about 30 to 40 minutes to heat 40-degree water up to 120 degrees. A 50-gallon unit will take about 40 to 50 minutes to heat up.
A large 80-gallon gas water heater takes about 60 to 70 minutes to heat up. Of course, this is just an estimate, and will vary by age and model.
How Long Does It Take an Electric Water Heater to Heat Up?
Electric water heaters take longer to heat up than gas units. These units use immersed electrical heating elements inside the tank to heat the water. They take about twice as long to heat up.
The time it takes is influenced by the heating element wattage and the temperature the water heater is set to. However, here are some averages:
- 40-gallon electric water heater: 60-80 minutes
- 50-gallon electric water heater: 145-150 minutes
- 80-gallon electric water heater: 120-130 minutes
If you have a 40-gallon, 5500-watt electric water heater and set it to 120 degrees, it will take about an hour to an hour and 20 minutes to heat up.
A 50-gallon electric unit will take about an hour and 45 to an hour and 50 minutes to heat up. For a large, 80-gallon electric water heater, it will take about 2 hours for the water to heat up.
6 Factors That Affect Water Heating Time
Now that you’ve seen that water heaters can take anywhere from about half an hour up to more than 2 hours to heat up, let’s look at the factors that affect how long it takes.
First-Hour Delivery Rate
All water heaters have a first-hour delivery (FHD) rating. The FHD indicates how many gallons of hot water the heater can provide in an hour when it is full. FHD rates are given in gallons per hour (GPH).
A high FHD rate means you’ll get more hot water sooner than you would from a unit with a lower FHD rate. For a 50-gallon unit, a FHD rate of about 60 to 80 GPH is good.
A water heater’s recovery rate is how many gallons of hot water the unit can provide per hour as it is being used. It tells you how quickly the water heater can recover (aka refill) with cold water and heat it up.
A unit with a high recovery rate will provide hot water faster because it takes less time to heat it up. So even if you’re using a lot of hot water at once, a water heater with a high recovery rate will be able to heat the incoming cold water quickly.
A water heater’s power source (gas or electricity) has a lot to do with how long it takes to heat water up.
Electric water heaters are known to take longer to heat water. This is because it’s less efficient to use electrical heating elements than gas burners.
Your average 50-gallon gas water heater might have a FHD rate of 80 to 90 GPH, but a 50-gallon electric water heater will have a FHD rate of about 58 to 66 GPH.
While you might have to wait about 30 minutes for an average gas water heater to heat all the water in the tank, you’ll have to wait twice that long for an electric model.
Water Heater Type
Storage water heaters are those with tanks that hold and heat water. Tankless water heaters don’t have storage tanks and heat the water right before it comes out of the tap.
There’s a huge difference in how long it takes these two types to heat water. A storage water heater takes anywhere from 30 minutes up to about an hour and a half to heat up.
A tankless water heater generally makes hot water available instantly. If too much hot water is being used at once, the flow rate (in gallons per minute) will drop, but the water that does come out will still be hot.
Water Heater Size
A storage water heater’s size, or gallon capacity, has a lot to do with how quickly it can heat water. Typically, storage water heaters can hold anywhere from about 30 to 80 gallons of water.
Smaller tanks heat water faster (and run out of hot water faster) because there are fewer gallons to heat. This is just like heating water in a small 2-qt. saucepan on the stove versus a full 12-qt. stock pot.
The water in the saucepan will boil faster. But larger tanks don’t take as long to heat up as you might think. Bigger electric models have two heating elements to help the process along.
Large capacity gas water heaters have a bigger gas burner to help them heat up quicker. Still, if you have a 30-gallon capacity water heater, you won’t wait as long for it to heat up as if you had a 50 or 80-gallon unit.
Original Water Temperature
The original water temperature has a lot to do with how long it takes for a unit to heat it up. If the inlet water temperature is low, the water heater must work harder to raise the water to the temperature you’ve chosen.
In colder climates, the inlet water temperature is usually about 40 degrees Fahrenheit. In warmer climates, it’s about 50 degrees. The water heater takes time to heat water from 40-50 degrees up to 140 degrees.
How Much Time Does It Take For A Water Heater To Heat Up?
If you have a gas water heater set to 120 degrees and the incoming water is about 50 degrees, you shouldn’t have to wait more than about 30-50 minutes for hot water (in 40 and 50-gallon units).
If you have a 5500-watt electric water heater set to 120 degrees and the incoming water temperature is about 50 degrees, you’ll have hot water after a little longer wait. It will take about an hour to an hour and 45 minutes (in 40 and 50-gallon units).
Generally, you should have hot water within less than 2 hours, no matter what type of water heater you have. If your water heater takes more than about 2 hours to heat up, call a professional to take a look.