a cartoon water heater with fire next to it, and money at the top right

Whether it’s for toasty showers or clean dishes, everyone needs hot water.

However, this daily life essential can use a lot of power and cost considerable money.

The key to mitigating these expenditures is understanding how much energy a hot water heater uses.

The average hot water heater uses roughly 4000 watts, making up 17 percent of a household’s energy expenditure. An array of factors impacts precisely how much energy an individual hot water tank uses and how much that, in turn, costs.

We take an in-depth look at these factors and discuss how to mitigate them.

Keep reading to learn what’s using your hot water and how to reduce waste.

We have a helpful article here if you’re interested in finding out about electric heat pump hot water heaters.

What Determines a Hot Water Heater’s Energy Usage?

A conventional hot water heater in the corner of a garage.
The amount of energy used by a conventional hot water heater is essential to bear in mind when considering the alternatives.

The average hot water heater uses about 4000 watts of energy, but individual units vary.

Factors impacting usage include:

  • The heater’s age
  • The size of the device
  • Daily hot water usage
  • The heater’s model
  • The temperature the heater is set to

Varying the above factors can have a significant impact on your energy consumption.

So let’s explore each factor a little further.

Age of the Heater

Older heaters use more energy to generate less hot water. While no one wants to replace a functional device, your heater is past its prime if it’s over 15 years old.

Hot water heaters older than 15 years lose efficiency and cost you money.

The Size of the Unit

Larger heater models use more energy. However, think carefully before replacing your large heater with a smaller one to save energy because you need a tank large enough to accommodate the needs of your household.

The typical requirements for different-sized households break down as follows:

  • One to four people: 40-gallon (151.42 liters) tank
  • Four to six people: 50-gallon (189.27 liters) tank
  • Six to eight people: 75-gallon ( 283.91 liters) tank

Daily Hot Water Use

Yellow rubber duck bath toy floating in a bath.
If you have a lot of baths, that’s likely to increase your hot water consumption considerably.

Water needs vary from home to home, but the Environmental Protection Agency estimates that most households need about 40 gallons (151.42 liters) of hot water daily.

That number goes up or down, contingent on the size of the household and individual needs.

This chart provides a breakdown of how much hot water is used for specific tasks:

ActivityHot Water Used
Hair Washing4 gallons (15.14 liters)
Flushing the toilet (per flush)1-2 gallons (3.79 – 7.570 liters)
Handwashing dishes9-27 gallons (34.07- 102.21 liters)  
Tooth brushing1 gallon (3.79 liters)  
Dishwasher machine6-16 gallons (22.71- 60.57 liters)
Laundry (per load)25-40 gallons ( 94.4 – 151.42 liters)
Bath36 gallons (136.28 liters)

These numbers are approximate but provide a basis for a reasonable water usage estimate.

Model Type

Hot water heaters come in two varieties: tankless (or on-demand) and tank heaters.

Tank models heat the water whether or not you will use it. As the name suggests, on-demand water heaters wait until the hot water is needed to warm it up.

On-demand models are more energy efficient since they allow for the fact that water usage varies from day to day.

For more information about the pros and cons of tankless water heaters, please read our article here.

Water Temperature

Most tanks raise your water’s temperature to 140 degrees Fahrenheit (60 degrees Celsius).

However, reducing your water heater’s temperature to 120 degrees Fahrenheit (49 degrees Celsius) saves energy and money. Reducing the temperature like this lowers energy consumption by 6-10 percent.

Reducing a water heater’s temperature from 120 to 90 degrees Fahrenheit (49 to 32 degrees Celsius) saves a further ten percent – or 41 dollars – yearly.

Such a drastic reduction in temperature is not normally recommended, though, because scientists warn that water below 120 degrees Fahrenheit isn’t effective at killing bacteria.

Energy Factor

The Energy Factor – or EF- rating determines how much hot water your tank can make, given its current wattage.

Look for high EF ratings, which will considerably reduce your power consumption and cost.

You want to aim for an EF between 0.5 and 0.7.

How Many Hours a Day Does Your Hot Water Heater Run?

Hot water faucet running.
The more you use your hot water, the more your hot water heater will need to run to keep up with demand.

A hot water heater’s active hours directly impact energy usage.

Most devices run between three and five hours per day; however, a range of factors influence running time, including:

  • The heater model
  • How many people it serves
  • How much water does the tank store
  • What temperature it’s set to
  • How efficient the heater is

The various activities and devices relying on hot water also dictate how long your heater runs.

What’s Using My Hot Water?

While hot showers and hand washing use a large quantity of hot water, some hidden sources also draw warm water from your heater.

Generally speaking, outdated appliances waste more hot water.

Consider upgrading to newer devices, and look for the Energy Star label, which indicates that the machine uses less energy.

Let’s look at some common appliances that use hot water.


Showere head mounted on a tiled wall.
Did you know you can save money on hot water usage just by changing the type of shower head you use?

Showers immediately leap to mind when we consider hot water usage.

The Environmental Protection Agency estimates that families use 40 gallons (151 liters) of water daily on showers.

Several variables impact that number, however, including:

  • Family size
  • Shower temperature
  • Shower length
  • Showerhead type

Consider upgrading older shower heads to conserve energy.

Standard models use 2.5 gallons (9.5 liters) of water each minute, while Water Sense labeled heads use two at most.

Water Sense fixtures can save families up to 2,700 gallons (10,220 liters) of water annually.

Washing Machines

Showers use considerable hot water, but the greatest offender by far is the common clothes washer.

According to the United States Department of Energy, washing machines use 25 gallons (95 liters) of hot water per use.

Fortunately, many washers allow you to regulate the water temperature. If you’re in the market for a new, more energy-efficient washing machine, consider these factors:

  • Temperature controls: Adjusting the water temperature, particularly during rinsing, saves energy
  • Load capacity: Small capacity washers use less energy
  • Loading: Front load washers use less energy than top loaders


Most of us assume that handwashing dishes saves water. However, an energy-efficient dishwasher conserves energy and can save you money on this task.

Dishwashers come in two sizes: standard capacity and compact capacity.

Compact capacity is best for small households with few dishes, but it may require multiple cycle runs for large quantities of dishes, canceling out any energy savings.

Additionally, many dishwashers have a heat boost that raises the water temperature to 140 degrees Fahrenheit (60 degrees Celsius) as it enters the machine.

The heat boost reduces the work of your hot water heater and conserves energy.


A dripping chrome faucet.
A leaking faucet can waste a lot of hot water over the course of a year.

A drippy faucet may seem like little more than a passing irritation. But unfortunately, leaky fixtures cost energy and money.

Leaks occur in faucets, pipes, and showerheads, allowing plenty of opportunities for water to go to waste.

While it’s difficult to imagine such small amounts of water using much power, a constant small leak can cost you up to 35 dollars a year.

This cost isn’t devastating, but you can easily avoid it by repairing the leak.

How To Use Less Hot Water Daily

Using less hot water is better for the environment. It also saves you money.

Many small steps can help reduce the energy a hot water heater uses.

Try these simple steps:

  • Install low-flow shower heads/faucets
  • Use cold water when you can
  • Turn off the water when you can while brushing your teeth and shaving
  • Take fast showers
  • Skip baths
  • Buy a newer hot water heater
  • Use an insulation blanket to keep the heat in your tank
  • Make sure your washing machine and dishwasher are working correctly and efficiently
  • Use the dishwasher if you have one

How Much Does My Hot Water Heater Cost Me Daily?

A calculator displaying the word "cost" sitting on a table covered with charts and a pen.
Calculating the cost of hot water heating is easy if you know the right equations to use.

Hot water is a necessity of daily life. However, it can be an expensive one.

It’s easy to take hot water for granted when it’s accessible with just the turn of a faucet. Yet, it’s important to remember that the piping hot liquid is costing you.

The extent of the expense is influenced according to whether your heater is fueled by electricity or gas.

Electric Heaters

Figure out the cost of your hot water with the following equation:

daily cost = (watt usage × price per kilowatt hour × active daily hours) / 1000

Using the averages of three daily hours, assuming a 4000-watt heater and ten cents per kilowatt-hour, hot water costs breakdown to:

  • $1.20 a day
  • $36.50 a month
  • $438 yearly

Gas Heaters

Gas heaters are often cheaper, but the expense hinges entirely on the cost of natural gas, which can vary wildly, especially during periods of market shortage.

These models use a similar equation to the electric models, as follows.

cost = hourly therm usage × hours heater runs × price per therm


Hot water heaters are requirements for daily living.

Their precise energy usage varies from model to model, depending on individual households.

Many factors impact the device’s power usage, ranging from the amount of water used daily to the temperature to which you heat the water.

Luckily, you can reduce the cost of your energy bill by managing your hot water usage wisely and bearing in mind the points set out in this article.

If you enjoyed this article, you might find our article entitled “Water Heaters: The 10 Best Ways to Save Energy” interesting for further information.

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