A water heater is more than likely one of the most important, yet the very least thought of, piece of equipment in your home. When considering a water heater, one thing you must think about is the amperage the new unit will use.

The amperage is critical to certain you do not overload your current home’s electrical system.

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The traditional amperage because that an electric water heater is 18.8 Amps with 240Volts, 4500 Watt. A gas water heater in typical uses less than 12 Amps with 115Volts (US and also Canada). However, the precise amount of amperage a heater provides depends on plenty of factors:

Heater TypeFuel TypeCapacityEnergy Efficiency

Understanding the quantity of amps a water heater needs is an important information for every homeowner. Through all the choices available, deciding ~ above a water heater deserve to be a difficult task.

However, when you understand the various choices described below, you will certainly make an informed decision.

Heater Type: Tank or Tankless

Water heaters work one of two ways: v a tank that stores water the is repeatedly heated or with coils that warm water on demand. 

Tank devices are also known together storage or container heaters. This units are the oldest and most traditional form of equipment.

Tankless tools are additionally known together on-demand heaters. These devices are newer in design.


In general, storage water heaters require less amps than tankless heaters. However, they might require an ext power all at once because they space constantly heating the water inside their tank.

Tankless heaters just run when there is a need and so their overall power draw may it is in less depending upon the quantity of actual use.

What size Breaker because that a 40-Gallon electrical Water Heater?

A 40-gallon tank is the most usual size of residential container heaters. So, if you are installing this size unit in an enlarge home, odds space you will be replacing a an in similar way sized unit. 

If an old unit is installed, the installer will have to remove the old unit and replace it through the brand-new one. No extra cost is normally required.

This size unit will usually require a 30-amp breaker, which is among the most typical size breakers supplied in residential homes. Due to the fact that of this, most homes will not need any kind of electric system upgrade once installing this type of device.


How numerous Amps go a Tankless Water Heater Use?

On average, one on-demand heater requires 120 amps to run, which is much higher than the traditional units that only require 30 amps to strength them.

Many older dwellings have 100 to 200 amps available and will call for an electrical system upgrade by a experienced electrician.

This upgrade may encompass your electrician adding a subpanel that circuit breakers to your home to boost the total amount that amperage available.

Fuel Type: electric or Gas

The type of fuel her water heater uses also affects the quantity of strength it needs to run effectively. A water heater will commonly run on electrical power or natural gas.

Electric Water Heaters

These types of units price less than gas units, yet they cost more to run them. This expense is because, overall, electrical power is an ext expensive than herbal gas.

On average, an electric water heater will certainly cost roughly $42 a month in energy use. 


However, this type of heater tends to be simpler to install due to the fact that it have the right to simply be attached to her home’s electrical system instead of having a gas line run.

How countless Amps does an electric Water Heater Use?

An electrical heater through a tank needs a 240-volt committed circuit v a 30-amp breaker. Since this type of machine requires a devoted circuit, an electrical upgrade may be necessary for her home.

A tankless electrical unit needs a 120-amp breaker. For plenty of older homes, this form of an equipment will require upgrading the electrical system. This upgrade is another added expense in up-front expenses when it involves on-demand water heaters.

Gas Water Heaters

Heaters that run on gas room usually 25 come 50% much more expensive than systems that operation on electricity. However, because they expense less to run, they often tend to consist of for the price difference over time.

On average, a gas water heater will cost approximately $30 a month because that an average house.


Because gas units have to be attached come a gas line, there might be an added expense as soon as installing together a an equipment for the very first time. This is specifically true if you need to run a brand-new gas line or upgrade your present natural gas system.

How numerous Amps go a Gas Water Heater Use?

A gas water heater through a tank will require 30 amps the electricity, which typically does not require any kind of kind of adjustments to the home’s electrical system–even for older dwellings with only a complete 100- or 200-amp service.

A tankless unit that runs on gas will need a 120-amp breaker. Due to the fact that of this kind of breaker’s high amperage, countless older residences will require changes to the electric system to accommodate this type of device.

Should You readjust Your Heater’s Fuel Type?

For plenty of people, they might think the if they currently have an electric water heater, it is impossible to install a gas unit or angry versa. This is no necessarily the case. 

If you room interested in changing the kind of equipment you have, every you need to do is ask an expert. Many electricians and plumbers offer complimentary consults. Uncover one in her area that does and simply ask them because that an evaluation.

If you room considering converting to natural gas, you can speak to your neighborhood gas provider and also find out if lock offer organization in your area. Some providers might even be able to give friend an calculation of the costs right over the phone.

When contemplating changing your water heater’s kind of fuel, take it the complying with questions into consideration:

Is the fuel form available in her location?How lot will the environment cost?Will the installation need a permit?Will you have to upgrade your homes full amperage?How lot will your monthly bill be because that this new fuel type?

Once you answer the over questions, girlfriend will understand whether transforming your heater’s fuel form is precious the time, effort, and money involved.

Though changing your heater’s fuel type may require much more work and also cost during installation, it may be more cost efficient for friend overall.


Water heaters space only beneficial when they carry out you with hot water as soon as you need it. Whether the unit has actually a tank or not, or runs on gas or electricity, if that is no the right size for your home’s water demands, the is no going to work-related for you.

The lot of power your heater draws additionally depends ~ above the capacity of her unit.

For instance, warehouse water heaters have actually a selection of 20- come 80-gallon size tanks. The bigger the tank, the more power it will take to warmth the water. 

A 40-gallon tank is usually sufficient for a 2- come 3-person household. It is recommended that you boost the dimension by 10 gallons because that each additional person you have in her home.

The capacity of on-demand heaters is calculated by gallons every minute or circulation rate. The higher the circulation rate, the more power the unit will draw at one time, and the higher your power or gas utility bill.

Calculating the circulation rate, friend will require for your house requires girlfriend to include the circulation rate needs of every of the fixtures you would desire to operation simultaneously. 

That is, if you desire to have the ability to take a shower, operation a fill of laundry, and also run the dishwasher at the very same time, friend must include the circulation rates of every of these tools together. 

Then you would pick a tankless heater that has actually a greater flow rate than the number you calculated. You can figure out which size heater will job-related for you making use of the Tankless Water Heater Sizing Diagram.

When it concerns heater capacity, that is an essential that you find a balance in between your household’s needs and also its electrical capability.

Choosing a unit that has actually the largest capacity easily accessible may sound appealing, yet it may require much more amps than your house is able to accommodate.

Energy Efficiency

Studies show that heating a home’s water accounts for about 18% of the home’s complete energy use.

How effectively your heater uses power will also affect how countless amps the unit uses. Usually, the much more energy-efficient the heater is, the an ext amps it will certainly need.

However, though a much more energy effective heater might require much more amperage to power on, the unit will be supplied for much less time and also save girlfriend money in energy prices overall.

An older item of tools usually has tendency to be less energy efficient. If your unit is end ten years old, the is time to think about replacing it through a more efficient model.

Electric water heaters have tendency to have greater energy effectiveness ratings 보다 gas units.

However, because gas usually costs less 보다 electricity, the two units often tend to break also cost-wise. 

When trying to find a brand-new heater, look because that the power star logo. This logo means that the unit meets the energy star standards. These tools tend come be much more energy-efficient and, in turn, an ext cost-efficient.


When you need it, having hot water is not just a luxury but a requirement in today’s day and also age. As such, you require to discover a unit that fits her budget–both in up-front costs and also in consistent use.

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It is additionally essential that you consider the lot of in its entirety energy your water heater will attract from your house to ensure your electrical system can handle the demand.