Enjoy free shipping and returns on all anodes!
  • Home
  • Blog
  • How long does a Water Heater take to Heat up?

How long does a Water Heater take to Heat up?

Published and updated
Rheem water heater models and buyer's guide

A question that is often asked by many homeowners. How long does it take for a hot water heater to heat water? The process is rather simple. If you can reset your water heater, the main thing has been done.

WARNING: Please ensure that the tank is full before plugging the HWH. The heating elements might burn out if this step is not carefully carried out.

The rest will depend on the following:

How long does hot water take to come back?

Even though, there are multiple factors leading to this question, it will mainly depend on 2 factors:

  1. types of hot water heater
  2. tank capacity (water in the tank)

In general, most water heaters will heat up anywhere between 30 to 120 minutes after resetting or as recovery time. Let’s explore the multiple factors in play.

The hot water heater types

Mainly, there are 4 types of water heaters:

  1. Electric
  2. Oil/Gas
  3. Tankless (hot water on-demand)
  4. Solar

How long for electric hot water heaters to heat up:

Electrical heaters take longer to heat up. For instance, it would take between 60-70 minutes for a 40-gallon electric water heater to heat after resetting.

From cold water:

  • 40 gallons: 60-70 minutes
  • 50 gallons: 70-80 minutes
  • 60 gallons: 80-100 minutes
  • 80 gallons: 120 minutes and more

How long for Oil/Gas tank water heaters to heat up:

After resetting, gas water heaters will take between 30 and 40 minutes to heat the water. As a general rule, if the BTU rating is high, water heating will be speedy.

From cold water:

  • 40 gallons: 30-40 minutes
  • 50 gallons: 40-50 minutes
  • 60 gallons: 50-60 minutes
  • 80 gallons: 60-70 minutes

Gas: To avoid entering full-blown thermo-dynamics calculations, a rule of thumb is:

For instance, let’s take a 40,000 BTU system with a 40-gallon tank.

TIME: 45 seconds to heat 1 gallon, leading to a 30 minutes to heat up the tank.

How long for Tankless water heaters to heat up:

A tankless water heater heats the water in a fraction of seconds after resetting. Most of them will heat the water anywhere between 15-20 seconds. The amount of time is trivial.


The soloar and geothermal systems are almost identical to the electrical water heaters. However, they may take up more time to heat the water without a power storage system or on cloudy days.

Other important factors

The tank capacity (size) and the type (electric, gas, oil, tankless, solar) are the 2 main factors. In addition, there are others that come into play and they might be rather significant. Let’s explore them one by one, shall we?

Maintenance, maintenance, maintenance!

Corrosion is a target goal in terms of issues to look out for. By definition, corrosion is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. As the hot water heater is always in contact with a mix of oxygen and water, the corrosion inevitably takes place. Water heaters are intented to fight against corrosion through different methods.

The glass-lined interior, the temperature and relief valve and the sacrificial anode are all methods to help stop corrosion. But sediments will gather at the bottom of the tank and coat the elements. This situation will refrain the heating elements from releasing heat at the optimal capacity.

Always, protect your hot water heater from corrosion and the best way is with cathodic protection. Install a Corro-Protec powerered anode and your heater will last beyond your expectation.

Thermostat settings

If both thermostats are set on HIGH, the water will heat up faster than if they are set on AVERAGE. However, it might not make that much of a difference in the long run. You don’t want to burn the elements out. Nobody wants to wait for hot water to come along.

The sizes of the heating elements

Size is important but accordingly and in moderation. The size of the elements should be chosen in agreement with the needs of the household. However, the bigger the elements, the faster the water will heat up.

Water temperature coming in (inlet water)

The incoming temperature can also impact on the heating time.

Let’s imagine that you live in a cold region where water temperatures are often below zero! It will obviously take longer to heat up the water temperature to 120-140 degrees Fahrenheit.

Now, try to imagine comparing an incoming water temperature of 55 degrees to one of 27 degrees Fahrenheit? The colder the water comes in, the longer it takes for the water heater to heat the water up. That’s a no brainer.

Pipe insulation

Improve the efficiency of your hot water by insulating the pipes. It will help to keep heat from escaping as the water runs from the heater to your faucets. Pipe insulation can easily be found at most hardware stores.

How long for hot water heaters to refill

Just before concluding, let’s quickly address the refilling aspect. The time it will take for your hot water heater to refill depends on the water pressure of the home. But as a general rule, it will take 30-40 minutes for a 40-gallon tank to fill up (1 minute/gallon).

Final word

It will take most heaters 1 minute per gallon to heat up but many factors are in play. Do not underrate maintenance of your equipement as corrosion is a serious issue in terms of recovery time and system effectiveness.

Look up the information above again if need be and enjoy endless supply of hot water.


Leave a comment

Your email address will not be published.


Hot Water Heater Not Working ? Here’s 9 Reasons Why!

Hot Water Heater Not Working Well? We work so hard all day, and getting home to a great shower is our little slice of heaven. […]

Hot Water Temperature : Avoid Setting Your Water Too Hot

If your hot water temperature is set to 140 degrees Fahrenheit, it takes three seconds to burn your skin serious enough to require surgery. Three seconds isn’t long at all. […]