How Long Does it Take a Traditional Water Heater to Heat Up?

If you have a new water heater you will ask yourself just how long it will take to warm up?

The average time for a traditional water heater to heat up the water and enable you to have a hot shower between 30 to 40 minutes. Time may increase with the increase of the water heater tank size.

If you live in a family household, you probably want to plan your water use and activities, so we will take a closer look at how long it takes a water heater to heat up.

Initial Heating Times per Water Heater Type

shower head with hot water

If you have a gas water heater it will heat up a bit faster than an electric heater. Following installation, your gas heater will heat up for the first use in 30-40 minutes. However, your new electric heater when heating for the first time will take 60 minutes, and sometimes longer.

A tank heater is used to store heat for different reasons and measuring the heat of the water differs in different countries depending on whether you think in gallons or metric.

Factors that Affect the Heating Speed

  • size of the heater
  • season, it takes longer to heat up in winter, because it starts from a lower point. In summer, water will heat faster.
  • the flow rate of water
  • distance of the tank from the shower

Gas Water Heater

For example a 40-gallon gas tank, the water will heat up in thirty minutes, heating at a rate of 30 seconds per gallon. if you want to make it quicker you can turn the gas up higher.

Electric Gas Water Heater

Your 40-gallon electric tank of this size will take a little longer to heat, as the smaller the tank the faster it will heat, and this size will take around 45 minutes to be hot enough for a shower in winter.

Water Heater Tank Sizes

The standard sizes for horizontal hot water tanks range from 180-3500 gallons, but 180 gallons is too big for a small family, so we will look at calculating the correct size.

A family of four will require a 50-gallon tank, if you decide to go smaller this is a false economy as the tank will overwork and probably break down.

If you want to calculate how much hot water you actually use, read the water meter, write down the reading taking it again a month later and subtract the first reading then deduct about one-third for cold water use, this will give you a rough calculation of your monthly water use. It will give you a good idea of how big a tank you need.

Of course, some times of day are busier than others and can be considered peak- hours. For instance, if you are all getting up, showering, between 6-8 am, doing laundry, and then leaving the house for the day, peak hour is in the morning when you are using your most water.

Below is a rough calculation of the size of the water tank you will need based on the size of your family.

Family Size People and Capacity of Water heater

Family Size/PersonWater Heater Tank Size/Gallons
1 to 223-36
2 to 336-46
3 to 446-56
4 to 656-80
6 to 780-100
7 or More100

If you do have that peak hour demand, using several appliances like the washing machine and dishwasher all at once you will require a bigger tank than indicated.

If you have a hot tub get a 100-gallon tank, as hot tubs use a lot of water. The biggest hot water tank holds about 3,500 gallons and can be solar powered if you have the panels on the roof.

Gas Versus Electric Hot Water

In many places, hot water uses 25% of your home’s power, so unless you have solar panels using gas will save money. When you are comparing gas and electric hot water units, you may choose to run your unit off-peak. The regulatory health bodies and the WHO World Health Organization

recommend that stored water is kept at 60 degrees Centigrade to avoid the growth of harmful bacteria like Legionella a respiratory disease that can lead to pneumonia. So it is important to prevent the temperature (often at the bottom of the tank) from falling too low.

Gas Storage Hot Water Systems

A gas storage hot water system looks like an electric tank, but the main difference is an electric element is replaced by a gas burner.

These units are highly energy-efficient and choosing one with a 5-star rating also means lower greenhouse emissions.

Also with gas, there is no premium time of day excess charged, meaning peak hour won’t cost more for your water heater to operate.

Installation is quick usually achieved in a couple of hours.

When deciding between a gas and electric hot water heat and both are quite big, and both offer rebates for using energy/water-efficient showerheads and tapware. So it is important to decide which suits your family’s needs the best. The gas will heat up in around 40 minutes.

Electric Solar Systems

You may already have solar panels on the roof and decide that an electric water heater best suits your needs. Solar systems are equipped with a booster for periods of low light.

It is essential that you purchase a solar system with enough panels and tank storage this will avoid overuse of the booster, and keep the running costs down.

Once your solar system is properly set up, it will reduce the cost You may not need to use the booster much if you live in the right climate, with lots of sunshine. Your electric heater will heat up in 45 minutes, and be hot enough to shower.

If you have a garden there is always a part on the side of the house that is not used much. If you have a small house, you can install the tank outside, and plumb it straight into the bathroom, this way the tank won’t take up valuable indoor space.


The right water heater can be a difficult choice for the growing family, and as our families grow the need for hot water increases, so if you are just starting out in a new home, as a young couple, it may be a good idea to plan for a future when there will be more people in the house.