How Many Amps For Tankless Water Heater?

How many amps does a tankless water heater draw?

  • As an Amazon Associate, I may get a commission on eligible purchases made by you at no additional cost to you. will direct you to Amazon for all of the goods that are recommended on the site. Throughout recent years, tankless water heaters have received a tremendous amount of attention, largely due to its capacity to offer you with an almost unlimited supply of hot water. Nevertheless, you must also be aware of the necessities, which include knowing how many amps a gas tankless water heater consumes in order to operate properly. The installation of an electric tankless water heater will almost certainly necessitate an upgrade in electric service. Ten wires and a 30-amp circuit breaker are required to run a tank water heater with 4,500-watt components.
  • An entire home tankless water heater contains four 7,000-watt components, resulting in a total electrical load of 28,000 watts for one unit of electricity. This load necessitates the installation of cable and a circuit breaker capable of handling at least 120 amps, at a cost that is several times more than that of providing electrical service to a traditional tank water heater.
  • So, how much electricity does a tankless water heater consume?
  • In order to function properly, the average electric tankless water heater requires at least 120 amps.
  • Unfortunately, the overall capacity of the ordinary home is just 200 amps.
  • You’ll have to improve your electrical system to match the increased load demand, which is what it really implies.
  • Not only that, but the increased load would need the installation of a larger, more expensive meter loop and main panel for the residence.
  • Nonetheless, you as the end customer may be responsible for the cost of the wire that connects the neighborhood distribution transformer and the electric meter.
  • Tankless heaters may draw anywhere from 42 amps to 167 amps, depending on their size.
  • You can figure out how many amps your tankless water heater consumes by doing some math on your own.
  • Let’s take a short look at the math involved here.
  • A typical electric tankless water heater may produce power of between 10,000 watts (10 kW) to 40, 000 watts (40, 000 kW) (40 kW).
  • Almost all electric tankless water heaters work on a 240-volt circuit in order to limit the amount of electricity consumed.

In order to compute the using the electric power equation (P = IV), we must first express the I (or electric current) in the following way: I (amps) = P (watts) / V (volts) (volts) Example: Consider the following scenario: a 30 kW tankless water heater is connected to a 240-volt circuit.In what range of amps does a 30 kW tankless water heater operate at?The electrical power equation is used in the following manner: In amps, 30,000 Watts divided by 240 Volts is 125 amps.A heater of this nature consumes 125 amps (you need several 20-amp or 30-amp breakers for installation).It is self-explanatory in terms of the amount of amps that your tankless water heater will consume, and it is based on the calculation described above.

  • HVAC Metrix (Heating, Ventilation, and Air Conditioning) SEER = (1 EER100 percent + 42 EER75 percent + 45 EER50 percent + 12 EER250 percent)/100 EER = BTUcooling/W EER = BTUcooling/W HSPF = BTUheating/W = BTUheating/W COP is defined as Q (useful heat) divided by W.
  • (input work) Air conditioning capacity (ACH) = CFM x 60/Area x Heightceiling CFM x h = 4.5 times the total heat (BTU/hr) (std.
  • air) Temperature Sensitive Heat (BTU/hr) = 1.1 times the CFM times the time (std.

air) The latent heat (BTU/hr) is equal to 0.69 x CFM x gr (std.air) 1 horsepower is equal to 746 watts.1 kW is equal to 3413 BTU.So, you might be asking, how can I determine whether or not my home’s electrical system requires an upgrade, right?

  1. For starters, whether you’re a first-time buyer or an experienced business owner, hiring a trained expert and receiving full feedback on your house electric system is the greatest course of action you can take in order to avoid any last-minute mishaps.
  2. Just so you’re aware, if you’re intending to replace your conventional water heater with a tankless equivalent in your existing house, the installation costs will be significantly more than they would have been if you’d chosen to build the tankless heater from scratch.
  3. Suppose I install the new tankless water heater without first updating my home’s electrical system.

What would be the result of this?Absolutely, this is a fascinating and experimental issue that is difficult to respond to if you haven’t had any prior experience with the installation of a tankless water heater.Low voltage or rapid voltage reductions, on the other hand, are likely to result in dimming or flickering lights, as well as a variety of other issues.In layman’s terms, the user experience, convenience, performance, and efficiency would all suffer as a result of the change.Trust me, I’ve encountered issues such as flashing lights in the past, and after conducting a root cause study, I discovered that connecting 28-kW tankless units in houses with 150-amp services to 10-kW transformers was a clerical error on my part.

Gas Tankless vs. Electric Tankless: Which model requires up-gradation of a home electric system?

  • To put it another way, it ALL DEPENDS.
  • But, I’m confident that you aren’t here to accept this response, are you?
  • Let’s conduct some further study and delve a little deeper into the subject.
  • Simply said, based on my knowledge and experience, I can state that a gas tankless system does not often necessitate the upgrade of a home’s electric system, as an electric tankless system does.
  • I believe this is true.
  • Also important to note is that the majority of the gas tankless water heaters that we’ve examined on this blog have earned the Energy Star certification, and many of them are even eligible for federal tax incentives.
  • Although conventional heaters do not qualify for the Energy Star designation, this does not rule out the use of traditional heaters in the evaluation of an appliance based on its efficiency.

How many amps does a Rinnai tankless water heater use?

To be quite honest, Rinnai tankless water heaters are among the finest in their respective categories. The firm has proven its mettle time and time again by supplying cost-effective, high-efficiency goods, such as tankless water heaters, to its customers. Rinnai Tankless Water Heaters require 120 volts alternating current at 60 hertz and less than three amps to operate.

Are tankless water heaters 110 or 220?

  • Tankless water heaters are available in both 110V and 220V types, so you’ll be able to pick one that suits your needs.
  • As a result, you may select the one that is most compatible with your household electrical requirements.
  • The tiny tankless variant, that is, the point-of-use or under-sink tankless heaters, consumes the majority of the 110V power supply voltage.
  • Those strong tankless heaters designed for commercial use, on the other hand, require significantly higher voltages.

How many amps is a 50-gallon water heater?

A common electric tankless water heater operates at a maximum power of 4500 watts. Many of you may not be aware that 4500 watts is equal to 18.75 amps in a 240-volt electric circuit, which is something that many of us take for granted.

Are most hot water heaters 220?

The majority of electric hot water heaters operate on alternating current (AC) voltages ranging from 220 to 250 volts. When purchasing a tankless water heater for your house that operates on 220 volts, you should be aware that this voltage in a home necessitates the installation of a double circuit breaker rated for the amperage demand of the hot water heater.

How many BTUs do I need for a tankless water heater?

Due to the significant amount of gas required to heat the water to a proper degree (usually between 150,000 and 200,000 BTUs), an ordinary home would require an upgrade in the size of the gas line to accommodate this requirement.

How many amps does an electric hot water heater use?

  • The majority of the electric tankless hot water heaters that we’ve tested on our site so far have required a dedicated 30-amp, 240-volt circuit breaker to function properly.
  • Electric water heaters necessitate the installation of a 240-volt dedicated circuit that serves only the water heater and none of the other appliances or devices on the circuit.
  • In most cases, the circuit wiring will consist of a 30-amp double-pole breaker and 10-2 non-metallic (NM) or multi-conductor (MC) cable.

What size breaker do I need for a 40-gallon electric water heater?

To be honest, the normal household 30- or 40-gallon water heater consumes around 4500 watts, and if my memory serves me correctly, they are often powered by a 30 A circuit breaker.

What size breaker do I need for a 4500-watt water heater?

  • The breaker is designed for 30 amps because this is an entirely resistive load (5500 watts at 240 voltage equals 23 amps), and the wire is 10 AWG because this is a completely resistive load.
  • Using your example, the elements are strapped for 4500 watts, which results in 18.75 amps of permanent draw.
  • Permanent draw loads should be designed at 80 percent of breaker capacity, therefore a 20 amp breaker is only capable of delivering 16 amps of permanent draw.

What size breaker do I need for a 3000-watt water heater?

240 volts may be supplied via a 14/2 cable and a 15 amp double pole breaker, which can power a 3000-watt induction motor.

What size breaker do I need for a 7500-watt heater?

7500 watts divided by 240 volts equals 31 amps, requiring a 40 amp circuit breaker.

What size breaker do I need for a 5500-watt water heater?

  • According to the calculations, a 5500-watt water heater is well within the safe maximum for a 30 amp breaker and a 10-gauge electrical cable.
  • When the temperature of a circuit breaker exceeds its rating, the circuit breaker trips.
  • A 30 amp breaker with a 10 gauge wire has an 80 percent safe maximum of 24 amps, which is equivalent to 24 amps.
  • 24 amps multiplied by 240 volts equals a safe maximum of 5760 watts.

Does an electric water heater require a disconnect?

An electric water heater does not require any type of disconnect other than a circuit breaker at the main panel or sub panel, nor does it require to be visible, according to the National Electrical Code (NEC).

Wrapping Up

  • First and foremost, I’d want to express my gratitude for remaining with us to the very end. Second, I would like to bring your attention to the fact that I, along with my core team, have attempted to answer some of the frequently asked questions, such as how many amps does a tankless water heater draw, in the most accurate and thorough manner that we were able. I hope you find this information useful. And, if you were pleased with our efforts and would like to express your gratitude to us, all you need to do is forward this information to those who could benefit from it. After all, isn’t it true that sharing is caring? Is it possible for vinegar to harm a hot water heater?
  • Are you interested in learning everything you can about tankless hot water heaters?
  • How long can you go without having hot water with a tankless water heater?
  • Exactly what size tankless water heater do I require?
  • Is it worthwhile to invest in a tankless water heater?
  • Will a single tankless water heater be sufficient for my home?
  • The advantages and disadvantages of tankless water heaters
  • How long does it take for a tankless water heater to pay for itself?

How Many Amps Does Water Heater Use?

  • It is likely that the water heater in your home is one of the most vital but least thought about pieces of equipment in your residence. When shopping for a new water heater, one factor to consider is the amount of electricity the new unit would consume. The amperage is critical in ensuring that you do not overload the electrical system of your present house. The normal amperage for an electric water heater is 18.8 amps at 240 volts and 4500 watts, according to the manufacturer. With 115Volts, the typical use of a gas water heater is less than 12 Amps (US and Canada). However, the actual amount of amperage that a heater consumes is dependent on a variety of factors, including: Heater type, fuel type, capacity, and energy efficiency are all important considerations.

It is critical for every homeowner to be aware of the quantity of amps required by their water heater. Making a decision on a water heater may be a difficult undertaking, especially with so many options available. In any case, after you have gained an understanding of the numerous possibilities discussed below, you will be able to make an educated selection.

Heater Type: Tank or Tankless

  • It is possible to use a water heater in one of two ways: with a tank that holds water that is continually heated or with coils that heat water as needed.
  • Tank heaters are often referred to as storage heaters or container heaters.
  • These pieces of equipment are the oldest and most conventional types of equipment available.
  • Tankless heaters are also referred to as on-demand heaters in some circles.
  • These units have a more recent design.

Storage water heaters, on average, consume less electricity than tankless water heaters. However, because they are continually heating the water within their tank, they may consume more electricity in total than other types of appliances. Given the tankless heaters only operate when necessary, their overall power consumption may be reduced, depending on the amount of actual use they get.

What Size Breaker for a 40-Gallon Electric Water Heater?

  • Among home container heaters, a 40-gallon tank is the most often seen size.
  • As a result, if you are installing this size unit in an older home, it is likely that you will be replacing a unit of comparable size.
  • An old unit will have to be removed and replaced with a new one if an installation decides to use an older unit.
  • In most cases, there is no additional charge.
  • This size unit will often require a 30-amp circuit breaker, which is one of the most common sizes of circuit breakers found in residential buildings.
  • Most homes will not require any form of electrical system update as a result of the installation of this type of gadget because of this.

How Many Amps Does a Tankless Water Heater Use?

  • On average, an on-demand heater consumes 120 amps of electricity to operate, which is significantly greater than the consumption of typical heaters, which consume just 30 amps.
  • Many older homes only have 100 to 200 amps of available power, necessitating the installation of a professional electrician to improve the electrical system.
  • During this upgrade, an electrician may recommend that you have a subpanel of circuit breakers installed in your home in order to improve the overall amount of amperage that is available.

Fuel Type: Electric or Gas

The type of fuel that your water heater burns has an impact on the quantity of electricity it requires to function properly. A water heater will often be powered by electricity or natural gas to operate.

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Electric Water Heaters

  • These sorts of units are less expensive to purchase than gas-powered units, but they are more expensive to operate.
  • This is due to the fact that electricity is generally more expensive than natural gas on a per-unit basis.
  • The energy consumption of an electric water heater is around $42 per month on average.
  • However, because it may be connected to your home’s electrical system rather than requiring the installation of a gas line, this sort of heater is typically less difficult to install.

How Many Amps Does an Electric Water Heater Use?

  • An electric heater with a tank necessitates the installation of a 240-volt dedicated circuit with a 30-amp fuse.
  • The fact that this type of equipment requires a dedicated circuit means that an electrical update for your home could be required.
  • A 120-amp circuit breaker is required for a tankless electric unit.
  • When installing this sort of gadget in an older home, the electrical system will need to be upgraded.
  • When it comes to on-demand water heaters, this improvement represents still another additional price in terms of up-front fees.

Gas Water Heaters

  • Heaters that run on gas are typically 25 to 50 percent more expensive than heaters that run on electricity, according to industry standards.
  • However, because they are less expensive to operate, they are more likely to make up for the price difference over the long term.
  • For the ordinary household, a gas water heater will cost around $30 per month on average.
  • Due to the fact that gas units must be connected to a gas line, there may be an additional cost associated with installing such a device for the first time.
  • This is especially true if you need to install a new natural gas line or improve your existing natural gas system to meet your needs.

How Many Amps Does a Gas Water Heater Use?

  • It will take 30 amps of electricity to power a gas water heater with a tank, which normally does not necessitate any changes to the home’s electrical system–even in older homes with just a total of 100 or 200 amps of service.
  • A tankless device that works on gas will necessitate the use of a 120-amp circuit breaker.
  • Because of the high amperage of this type of breaker, many older homes will require electrical system upgrades in order to support this sort of device.

Should You Change Your Heater’s Fuel Type?

  • Depending on who you ask, many people believe that if they currently have an electric water heater, it is difficult to switch to a gas one, or that the opposite is true. This isn’t always the case, of course. If you are interested in altering the sort of equipment you now have, all you need to do is consult with an expert. A large number of electricians and plumbers provide free consultations. Find a company in your neighborhood that performs this and just ask them to conduct an evaluation for you. Whether you’re thinking about switching to natural gas, you may check with your local gas supplier to see if they provide service in your region. Some carriers may even be able to offer you with an estimate of the expenses over the phone, if you ask nicely. When considering changing the fuel source for your water heater, ask yourself the following questions: Is the fuel type accessible in your area?
  • How much will the installation cost?
  • Will the installation necessitate the acquisition of a permit?
  • Does this new fuel type require you to update your home’s total amperage? How much will your monthly payment be for this new fuel type?

Once you have answered the questions above, you will be able to determine whether or not changing the fuel type of your heater is worth the time, effort, and money required. Changing the fuel type of your heater may necessitate more effort and expense during the installation process, but it may be more cost effective in the long run.


  • It is only when you have hot water when you need it that a water heater is truly beneficial.
  • Regardless of whether the unit has a tank or not, or whether it is powered by gas or electricity, if it is not the proper size for your household’s water needs, it will not function properly.
  • It is also dependent on the capacity of your heater as to how much power it will demand from it.
  • Storage water heaters, for example, come in a variety of tank sizes ranging from 20 to 80 gallons.
  • The larger the tank, the greater the amount of energy required to heat the water.
  • A 40-gallon tank is normally suitable for a family of two to three people.
  • You should increase the size of your water tank by 10 gallons for each new person that lives in your house.
  • The capacity of on-demand heaters is measured in gallons per minute (or flow rate) and is expressed as a percentage.
  • Your electricity or natural gas utility bill will rise in direct proportion to the amount of power the device consumes at any one moment.
  • In order to calculate the flow rate that you will require for your house, you must sum the flow rate requirements of each of the fixtures that you want to operate at the same time together.
  • To put it another way, if you want to be able to take a shower while also doing laundry and running the dishwasher, you must add the flow rates of each of these machines together.

Then you’d pick a tankless heater with a larger flow rate than the one you predicted….Using the Tankless Water Heater Sizing Diagram, you may determine which size heater will be most suitable for your needs.When it comes to heater capacity, it is critical that you strike a balance between the demands of your home and the electrical capacity of your heater.It may seem enticing to get a unit with the highest capacity available, but doing so may demand more amps than your home is capable of providing.

Energy Efficiency

  • According to studies, heating a home’s water accounts for around 18 percent of the overall energy consumed by the residence.
  • The efficiency with which your heater utilizes energy will also have an impact on the number of amps the device consumes.
  • Generally speaking, the more energy-efficient a heater is, the more amps it will require to operate.
  • However, even if a more energy efficient heater may take more amperage to turn on, the unit will be in use for a shorter period of time, resulting in a reduction in total energy expenditures.
  • A piece of equipment that is more than a decade old is often less energy efficient.
  • In the event that your unit is more than 10 years old, it may be time for you to consider upgrading to a more energy-efficient model.
  • Electric water heaters have a greater energy efficiency rating than gas water heaters, on average.
  • However, because natural gas is often less expensive than electricity, the two units are typically equal in terms of cost.
  • Keep an eye out for the Energy Star badge while shopping for a new heater.
  • This mark indicates that the device complies with the Energy Star requirements.
  • These gadgets have a tendency to be more energy efficient, which results in their being more cost effective.


  • Having access to hot water when you need it is no more a luxury, but rather a need in today’s day and age.
  • As a result, you must locate a unit that is within your budget, both in terms of up-front fees and ongoing operating expenses.
  • It is also critical to evaluate the total quantity of energy that your water heater will use from your home in order to verify that your electrical system is capable of handling the demand.

How Many Amps Does A Tankless Water Heater Use?

  • Tankless water heaters have received a lot of attention in recent years, mostly due to their ability to provide an almost endless supply of continuously warm water.
  • Nonetheless, you must be aware of the requirements, such as how many amps a tankless water heater consumes, to ensure that you do not overload your home’s current electrical system when doing so.
  • It takes a minimum of 120 amps for an electric unit to function properly, and the average dwelling has a total capacity of 200 amps.
  • This means that you will almost probably need to modify your home’s electrical infrastructure in order to accommodate a higher power load requirement.
  • Additionally, a huge and expensive motor loop and main panel will be required for the property.
  • However, the actual number of how many amps does a hot water heater draw is dependent on a variety of parameters, including the kind of heater, the type of fuel used, the energy efficiency of the heater, and the capacity of the heater.
  • It is possible that you as a customer will be responsible for the wiring that connects your meter to the community energy supply transformer on occasion.
  • It is possible that you are asking yourself, ″How can I determine whether or not my residence’s electrical system has to be elevated?″ Well, the best thing you can do is hire a competent expert and get his opinion on your electrical system in order to avoid any last-minute disasters from occurring.
  • If you want to upgrade from your standard tank-style water heater to a tankless machine in your older home, the installation costs will be significantly more than they would have been if you had installed the tankless appliance in a newer home………………………………….

How Many Amps Does A Tankless Water Heater Use?

  • Instantaneous water heaters consume between 42 and 167 amps.
  • However, an average device requires 120 amps to function properly, which is far greater than the 30 amps required by ordinary heaters to operate.
  • Older houses have 100 to 120 amps of electrical capacity, which means they will almost certainly require an update to their electrical system.
  • This update should only be carried out by a qualified technician.
  • He may need to install a subpanel for circuit breakers in your home in order to increase the overall number of amps accessible to you.
  • Furthermore, the size of the breaker and the gauge of the wire used should comply with the state, provincial, local, and national electrical codes in your region.
  • The placement of a subpanel is particularly crucial for these devices, especially if the unit is not within visual range of the principal electrical panel when it is installed.
  • Furthermore, the wiring must be strong enough to ensure a voltage drop of less than 3 percent while the system is under stress.
  • Although it may appear that the first expenditure is prohibitively expensive, it is important to remember that on-demand heaters are incredibly energy efficient.
  • Modern versions are up to 94 percent efficient in terms of energy use.
  • Having multiple electrical gadgets in your home means you will want a larger power system than you now have.

It does not rule out the use of electric machinery as a viable alternative.You’ll have to improve your electrical system as a result.On the other hand, a 28,000-watt whole-house tankless appliance will require a cable and circuit breaker that can handle 120 amps, which will be significantly more expensive than an electrical system for a tank-style device.Traditional units with 4500 watts require 30 amps and 10 wires to be installed.The number of amps that a gas tankless water heater consumes may now be a mystery to you.

  • If you have a gas heater, you should first consider your ventilation requirements, as well as the condition of your current gas line.
  • Some manufacturers provide gas emission kits that you may purchase in order to ensure appropriate installation.
  • The amps required by gasless machines are small, requiring only the bare minimum of electrical connections.

When purchasing a model, make sure to look into the installation requirements of the model.

How Many Amps Does A Hot Water Heater Draw?

This chart can assist you in determining how many amps are necessary for a tankless water heater and what size breaker is required for the installation of an electric tankless water heater using the information provided.

Frequently Asked Questions

Q. Is 200 Amp Service Enough For Tankless Water Heater?

For them to work correctly, they require at least 120 amps of power, while the capacity of an older house is just 200 amps. As a result, it is necessary to improve the electrical system in order to accommodate the high load demand, which will cost roughly $1500.

Q. What Size Breaker For Electric Tankless Water Heater?

They’ll need a 40 to 50 amp breaker for each wire in the installation.

Q. Do Instant Water Heaters Need A Dedicated Breaker?

Yes, you will need to install three new circuit breakers to the inside panel as well as draw three new circuits from the existing ones. Many households do not have three vacant slots in the panel that would allow for the installation of the heater.

Q. Do Electric Water Heaters Require 220 Volts?

  • Many electric equipment operate at voltages ranging from 220 to 250 volts.
  • This voltage necessitates the use of a double circuit breaker that has been assessed in relation to the amp draw of the devices.
  • Conclusion Warm water is no longer considered an amenity, but rather a need in this day and age.
  • As a result, you must choose a model that matches your needs while also being within your budget—both in terms of upfront costs and ongoing expenses.
  • In addition, you must evaluate the total quantity of energy that your water heating system will need from your home in order to ensure that your present electrical service can manage the demand of the system.
  • Hopefully, our post on ″how many amps does a tankless water heater consume″ was informative.
  • If so, please forward this piece of information to people who may benefit from it.

How Many Amps Does A Tankless Water Heater Use? (42-167 Amps)

  • Electric tankless heaters heat water solely with electricity and do not need any other fuel.
  • As we all know, boiling water is a time-consuming and difficult operation.
  • As a result, electric tankless water heaters demand a large amount of electricity current, measured in amps.
  • Tankless water heaters consume a certain amount of electricity.
  • Tankless heaters may draw anywhere from 42 amps to 167 amps, depending on their design.
  • We can compute exactly how many amps a tankless water heater consumes since we understand two important factors:
  1. The total amount of power, measured in watts. Voltage and power input for electric tankless water heaters can range from 10,000W (10 kW) to 40,000W (40 kW)
  2. and temperature. All electric tankless water heaters run on a 240-volt circuit in order to limit the amount of electricity consumed.
  • In order to compute the using the electric power equation (P = IV), we must first express the I (or electric current) in the following way: P (watts) / V (amps) = I (amps) (volts) Example: Consider the following scenario: a 30 kW tankless water heater is connected to a 240-volt circuit.
  • In what range of amps does a 30 kW tankless water heater operate at?
  • The electrical power equation is used in the following manner: In amps, 30,000 Watts divided by 240 Volts is 125 amps.
  • A heater of this nature consumes 125 amps (you need several 20-amp or 30-amp breakers for installation).
  • We evaluated the amp draws for tankless water heaters ranging in power from 10 kW to 40 kW and summarized them in the following table:
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How Many Amps Do 10-40 kW Electric Tankless Water Heaters Draw?

All of these estimates are based on the assumption that the heater is powered by a 240-volt circuit.

Tankless Heater Size (in kW) Electrical Current (in Amps)
10 kW 42 amps
11 kW 46 amps
12 kW 50 amps
13 kW 54 amps
14 kW 58 amps
15 kW 63 amps
16 kW 67 amps
17 kW 71 amps
18 kW 75 amps
19 kW 79 amps
20 kW 83 amps
21 kW 88 amps
22 kW 92 amps
23 kW 96 amps
24 kW 100 amps
25 kW 104 amps
26 kW 108 amps
27 kW 113 amps
28 kW 117 amps
29 kW 121 amps
30 kW 125 amps
31 kW 129 amps
32 kW 133 amps
33 kW 138 amps
34 kW 142 amps
35 kW 146 amps
36 kW 150 amps
37 kW 154 amps
38 kW 158 amps
39 kW 163 amps
40 kW 167 amps

You can correctly determine how many amps your tankless hot water heater consumes by using this amp draw table. After that, you can figure up how many amp breakers you’ll need for the installation process. Check out our top-ranked list of the most efficient tankless water heaters here if you’re looking for a tankless water heater to replace your current one.

How many amps does a gas tankless water heater use?

  • Unfortunately, the average electric tankless water heater requires at least 120 amps to run, while the average household has a total capacity of 200 amps, making it inefficient.
  • An entire home tankless water heater contains four 7,000-watt components, resulting in a total electrical load of 28,000 watts for one unit of electricity.
  • It is necessary to install wiring and a circuit breaker that can withstand at least 120 amps for this load, which will cost several times as much as the electrical service for a traditional tank water heater.
  • In the same vein, what size circuit breaker do I require for a tankless water heater?
  • 40-50 amperes Is it necessary to have a dedicated circuit for a gas tankless water heater in this case?
  • A very small quantity of electricity is required to light the flame in a gas tankless water heater.
  • There is no requirement for a dedicated circuit unless the manufacturer specifies otherwise.
  • Is it true that a tankless water heater consumes less gas?
  • According to, ″demand (or tankless) water heaters can be 24 percent to 34 percent more energy efficient than conventional storage tank water heaters for homes that use 41 gallons or less of hot water daily.″ Demand (or tankless) water heaters can be 24 percent to 34 percent more energy efficient than conventional storage tank water heaters.
  • Tankless water heaters (especially if they are gas-fueled) can save households more than $100 per year if they are kept in operation for a long time.

How many amps does a gas tankless water heater need?

  • Unfortunately, the average electric tankless water heater requires at least 120 amps to run, while the average household has a total capacity of 200 amps, making it inefficient.
  • Because of this, you will need to improve your electrical system in order to meet the increased load demand, which might cost you up to $1,500 in total.
  • Continue reading for the rest of the answer.
  • Is it necessary to have a dedicated circuit for a gas tankless water heater as a result?
  • A very small quantity of electricity is required to light the flame in a gas tankless water heater.
  • There is no requirement for a dedicated circuit unless the manufacturer specifies otherwise.
  • In the same vein, how many amps does a water heater consume?
  • A water heater of this sort must be treated as a continuous load, which means that the branch circuit must be estimated at 125 percent of the heater’s rated ampacity in order to be considered safe.
  • 4500/240 = 18.75 amps can be run on a 20 amp OCPD, however 18.75*125 percent = 23.4 amps necessitates a 25 or 30 amp circuit, depending on the manufacturer.
  • In this case, what size circuit breaker do I require for a tankless water heater?
  • 40-50 amperes What are the drawbacks of using a tankless water heating system?

The most significant downside of on-demand or instantaneous hot water heaters is the high initial investment required.The smaller units that are frequently seen will not be able to provide enough hot water to meet the needs of most families.They can only handle one faucet at a time, which is an issue if you want to take a shower while the dishwasher is in the dishwasher.

Tankless Gas Water Heater Electrical Requirements

Water heaters that do not require a storage tank, whether gas or electric, are extremely efficient when compared to standard water heaters.While a gas tankless unit utilizes propane to heat water, several sections of the water heating system still rely on electricity to function correctly.So, what are the electrical requirements for a tankless natural gas water heater, exactly?Most tankless gas water heaters require a 120-volt circuit with a 15-ampere or 20-ampere rating to power the electric pilot light and control board, respectively.The National Electrical Code specifies that instantaneous water heaters have circuits that are not more than 120 amperes in current and that are not more than 150 amperes in current protection.

Depending on whether you reside in an area with a 220 volt or a 110 volt power source, the electrical needs for your tankless gas water heater might differ significantly.The electrical needs of the circuit will be calculated depending on the wattage of each individual product or brand.Voltage ratings are available in four different voltage ranges: 208V, 120V, 240V, and 277V.

Electrical Requirements of a Tankless Gas Water Heater

National Electrical Code requires that tankless gas water heaters be equipped with a 15-20 ampere 120-volt electrical circuit that supplies power to the unit’s control board and ignition device.Because the control circuit is an independent load, the circuit ratings are determined by the setting of the circuit breaker.A propane tankless water heater is equipped with an electrical control circuit that guarantees that the appropriate amount of electricity is delivered to the control board.The control board measures the temperature of the water that is supplied into the tankless unit as well as the temperature of the water that exits the water heater and flows into the taps around the house.The operation of control boards is dependent on the presence of power.

When correctly powered in accordance with the NEC regulation, the control board is capable of regulating the amount of heat necessary to get water up to the appropriate temperature.Upon determining the required temperature level, the control board conducts an electrical ignition sequence, which results in the heating of water to the desired temperature and delivery of the heated water to the point of demand in the residence.In the case of Rinnai, Takagi, EcoSmart or Rheem tankless natural gas water heaters, the manufacturer will have calculated and defined the circuit size before you installed your water heaters.For example, Rinnai tankless water heaters have an electrical demand of 120 volts alternating current, 60 hertz, and less than three amps, making them ideal for small spaces.

The devices are often sent with thorough installation instructions to assist you or your technician in completing the installation correctly.

Electrical components in a tankless gas water heater

The majority of homeowners believe that a gas water heater will continue to operate in the event of a power loss. Despite the fact that the tankless unit does not utilize electricity as a fuel to heat the water, it may be dependent on some electric components in order to operate correctly. You’ll find the following electrical components in your tankless gas water heater:

Electric control board

The electric control board of a tankless gas water heater is an integral component of the unit.The information and communication between all electrical components in a series circuit are relayed and monitored by electric control boards.This is what enables for proper operation to take place without interruption or malfunctioning of any kind.The electric control board functions similarly to the personal computer unit of the water heating system.It requires energy to operate the water heater, which is why your gas instantaneous water heater may not function properly if there is a power outage in your neighborhood.

The temperature of the water flowing into the tankless unit is sensed by the electric control board, which then signals the tankless unit to switch on or off the burners based on the measured temperature.The gas valve, burner, and water temperature are all controlled by this circuit board, to put it simply.Here’s how your home’s hot water is delivered on demand:

Gas pilot light

In some types of any propane or natural gas hot water system, a gas pilot light is an inherent element of the gas safety mechanism, which is illuminated by the pilot light.The pilot light in your water heating system is a little flame that is maintained at all times.The electric control board is in charge of controlling the gas pilot light.When it is necessary to heat water, the pilot light is activated, which causes the burners to ignite and heat the water to the temperature specified by the control unit.Keep in mind that tankless gas water heaters heat water nearly on demand, which means they are more energy efficient than tank-style water heaters, which require more electricity to keep water at a consistent temperature throughout the day.

Electrical Requirements for Different Brands

According on the type and manufacturer, the electrical requirements for tankless gas water heaters might differ significantly.According to the heating requirements of each home, the heating capacity of these devices varies significantly.The result is that circuit breaker installations, electrical wire gauges, and resistance will all differ significantly.Takagi, Rinnai, Stiebel Eltron, Mitsubishi, and Eemax are just a few of the well-known brands available in the United States.It is critical to double-check their installation guides to ensure that you meet all of the electrical standards and avoid any potential safety issues.

The following are the electrical requirements for a few of the items:


Rinnai tankless water heaters require 120 volts alternating current at 60 hertz with a current of less than 3 amps.As a result, it can only be used in the United States, Canada, Mexico, and portions of South America, and it has backward compatibility going back as far as 50 cycles.The tankless water heater must be connected to a 120-volt outlet and powered by 60Hz current.Tankless water heaters from Rinnai have a wide variety of electrical needs, from a 20 amp circuit breaker to the demand for multi-phase electricity.


  • Takagi tankless water heaters have electrical needs of 120 V alternating current 60 Hz and take less than 2 Amperes of power. The outlet must be connected to a dedicated circuit and should not consume more than 70% of the circuit’s total capacity, or the breaker would trip. When possible, use of a ground fault circuit interrupter (GFCI) outlet
  • however, if this is not practicable, an arc fault protection device (AFCD) that turns off electric current when it detects arcing inside the home’s wiring is needed by law. In order to assure the safety and legality of the installation, tankless gas water heaters should be installed by a certified electrician in your area, regardless of where you reside. Also recommended is having an electrical examination performed on your property prior to installing tankless gas water heater electrical requirements in order to detect any concerns that may occur as a result of its operation. ResourcesNational Electrical Code Style Manual
  • Takagi: Instantaneous Water Heater Installation Manual and Owner’s Guide
  • Thomas L. Harman, IAEI Magazine: Go Tankless.And Stay In Hot Water
  • Takagi: Instantaneous Water Heater Installation Manual and Owner’s Guide

How to Install a Tankless Water Heater

Instructions from a professional on how to remove an old water heater tank, prepare the area for installation of a tankless water heater, and finally install the tankless water heater Because it does not store a huge amount of heated water, a tankless water heater, also known as an on-demand water heater, saves money over a traditional water heater.Essentially, it serves to give hot water on demand, so you won’t have to worry about the shower suddenly being chilly.It should be noted that because a tankless water heater heats the water in real time as the water is being circulated, it can only heat a certain volume of water at a particular moment.Therefore, it may not function well in a family where two or three showers may be operating at the same time, as an example.The heating capacity of the unit will determine the maximum number of hot-water fixtures that may be served at any given time.

To do this job successfully, you will need strong plumbing abilities, and depending on your local codes, you may need a professional plumber to complete the task.For those who are capable of doing the task themselves, you should be familiar with how to turn off the water supply to your home (see How to Turn Off the Water to Fixtures) and how to cut into your supply pipes and attach new fittings and pipe to them (if you have copper pipes, see Cutting & Joining Copper Pipe).There are a few of fundamental choices: A tankless water heater that is fueled by gas and installed indoors must be vented to the outside.There is also the need for a gas line and an electrical connection to a 120-volt circuit.

A service panel can be hooked directly to the unit, or it can be plugged into an outlet.It is not necessary to vent an indoor electric tankless water heater to the outdoors because it is contained within the home.It does, however, require 240-volt electricity.It may either be hooked into a 240-volt outlet or directly attached to a power source such as a generator.

Tankless Water Heater Preparation

Remember to complete all essential preparations before disconnecting and removing your present water heater; you don’t want to be without hot water for a week or two while you wait for any plumbing, electrical, or vent work to be completed.If you are installing a new gas unit, you should determine whether you need to upgrade your gas meter.Because the unit consumes a considerable amount of BTUs, it is possible that your meter does not have the capacity to feed it in addition to the other gas-using appliances in your home.You should contact your gas company, which can inspect this for you and can generally upgrade the meter at little or no expense.Request that the gas provider inspect your new unit to ensure that it is receiving the appropriate amount of manifold pressure for it.

See also:  How To Turn Up Water Heater Temp

A 1-inch gas pipe from the meter to the water heater is often required for a tankless water heater.It is better to employ a professional plumber to install a new gas line if you need to replace an existing one.Prior to installing the unit, you may wish to have another gas shutdown valve installed.This will save you time and money.

Ventilation will be required for an inside gas unit as well.The fact that a tankless water heater generates a significant amount of condensation and pushes air out with a fan necessitates the installation of category II stainless-steel exhaust pipe with firmly sealed silicon joints, as seen in the second video below.The plastic pipe seen in the This Old House movie below may be appropriate for use with a high-efficiency tankless water heater, as demonstrated in the video below.A damper is an excellent addition for those who live in colder climates since it prevents chilly air from re-entering the home.You may also want to consider installing a condensate drain, which drains water from condensation through plastic tubing, depending on the make and type of your heater.

  • Floor drains and utility sinks should be used to dispose of the excess liquid.
  • All plumbing and venting needs should be determined by consulting the manufacturer’s documentation.
  • In addition to gas, a gas unit requires 120-volt electrical power.

Plan to either connect it into a nearby outlet or wire it straight to a junction box to avoid tripping over it.You can watch this wonderful video from This Old House, which will provide you with an excellent explanation of the many stages involved in installing a tankless water heater.This in-depth video, produced by Ron Hazelton, describes how a failed conventional water heater can result in debris in your water, which can clog faucet aerators, shower heads, and other water-using equipment in your home.He makes the decision to remove and replace his malfunctioning water heater with a tankless water heater, and he guides us through the entire procedure with his hands on assistance.

If you are installing an electric water heater that requires 240-volt electrical power, you should have an electrician route the wire to it unless you are confident in your ability to do so yourself.Codes demand that a subpanel (which may or may not be included with the unit) be erected next to the unit in order to comply.This subpanel is equipped with its own circuit breakers, allowing you to rapidly turn off the power to the device if necessary.Connect the wire to the subpanel and then from the subpanel to the unit, starting at the unit.

  1. It is essential that the electricity to the water heater’s circuit is turned off at all times while the work is being performed.
  2. +Find a Water Heater Installation Specialist in Your Area

Removing the Old Water Heater

In the majority of circumstances, a new tankless water heater will be installed in lieu of an existing storage water heater.In Ron Hazelton’s video above, he refers to our website for the directions, which are as follows: How to Flush or Drain a Water Heater (with Pictures).In order to remove the old water heater, turn off the valves on the two water lines (one for the input and one for the output) that lead into the existing water heater and disconnect them.To remove and detach the water heater’s lines from the water heater, use channel-type pliers or a pipe wrench.Drain the tank by opening the drain valve located at the bottom.

On a gas-powered unit, turn off the gas line valve and remove the gas line from the device.A segment or two of vent pipe should be disconnected and removed.If the device is powered by electricity, you may want to call an electrician to disconnect the wire since 240-volt power can be a potential source of electrocution.If you decide to handle it yourself, cut off the circuit at the service panel and check to be that the power has been turned off completely.

Remove the old water heater from the unit by disconnecting the cables from the unit.If you require assistance with this project, contact a local water heater professional.

Installing a Tankless Water Heater

Tankless units can be fitted flush against the wall (against the drywall or plaster), or they can be inserted into the wall between the studs.Using a stud finder, identify the studs in the wall where you want to install the unit, and then cut a hole between each of them.Attach the item to the wall in accordance with the manufacturer’s recommendations.Water supply pipes should be routed to the water heater.Make certain that the pipe from the water utility is linked to the inlet and that the pipe flowing to the home is connected to the outlet before starting the project.

Install shutdown valves on both lines near the unit, one on either side of the unit.You might also want to consider installing a pressure-relief valve.To complete the final connections to the inlet and outlet, union fittings should be used.The water valves should be opened, but not those for the power or gas.

Open all of the faucets in the house and let the water run through the unit for about a minute.Close the water valves and turn off the water.Remove the inline filter, which is normally placed near the intake, and thoroughly clean it to ensure that no debris is left behind.Replace the filter, turn on the water valves, turn on the electrical power, and turn on the gas valves if necessary.Finally, test the equipment to ensure that it is in proper functioning condition.

  • Resource Highlighted: Find a Pre-Screened Water Heater Pro in Your AreaCall today for free estimates from pre-screened water heater professionals in your area: 1-866-342-3263

Can I replace a 30A breaker with a 40A breaker for a new water heater?

Sure!If you aren’t concerned about your house burning down, then go ahead.Alternatively, it can be set on fire.Either that, or death.It is the same way that brakes and tires are matched to the cars on which they are placed that breakers are matched to wiring.

Excess electricity passing through the system is protected from you by the 30A circuit breaker.Installing a 40A breaker raises the limit on the amount of current that may be drawn.In this case, more current can flow than your wire can handle, resulting in the generation of heat in the wiring.If you run the circuit at 39A for an extended period of time, your wires may melt or catch fire if you are unlucky.

The breaker, on the other hand, will not trip because it is rated for 40A.Some people have suggested that your wiring may have been overspecced from the start, enabling for a 40A breaker to be installed without issue.Okay, but who would do anything like that and why?Installed as a complete system, your electrical system is intended to function as a cohesive one.Overpaying for wiring by installing higher-rated wire is not widely practiced!

  • Consider the following scenario: It’s as simple as swapping out a 30A breaker with a 40A breaker.
  • It is possible that you are permitting the whole system (and not simply the breaker) to operate at a rate that is 33 percent higher than its rated capability.
  • Suppose about it: what do you think happens to your safety margin when you do anything like that?

Now that you’re dancing with Pele, there is no such thing as a safety buffer.

What Size Breaker for a Hot Water Heater: A Breaker Size Solution

Is your electrical water heater tripping the breaker on a regular basis?Is it possible that your heater overheated without you noticing?You have clearly indicated that you are experiencing difficulties in matching your appliance with its safety device based on just a few questions.What size breaker do you recommend for a hot water heater, I hear you ask?For the most part, 30-amps is the common size for heaters.

It is important to note that this breaker ampacity does not necessarily work for every water heater available.There is a formula for determining the proper breaker size, but there are other important aspects to consider, which we will discuss later in this article.

Understanding Your Water Heater

When purchasing an electric water heater, one of the most common mistakes made by homeowners is failing to verify the amperage rating of the unit.Some heater tanks are just labeled with the voltage and wattage requirements, but not with the ampacity requirements.It is preferable if you obtain your tank specs from the shop or the brand manufacturer directly themselves.The size of your heater must serve as the foundation for establishing the appropriate breaker size.The following are the three criteria you should examine in order to assure your safety: Voltage- The volts provided by your boiler are critical to the operation of a properly functioning circuit.

Depending on the size of your tank and the power of your heater, you can connect it to a 220 or 240 Volt outlet.Wattage- Include the wattage requirements for your heater in your list.Knowing the wattage of your gadget is extremely beneficial if your equipment often consumes a large amount of power due to its tank size and other features.It will assist you in your quest for a proper breaker to manage the situation.

Wire Size- Finally, it is critical to understand which cable type is suitable with the breaker size of your hot water heater system.An mismatched size or broken cables that have been reused might put your heater and breaker at greater risk than they are worth.

A Breaker Size Solution: What’s the Formula?

If you’re unsure of the amp size you’ll need, doing a simple calculation will provide the answers you need.Knowing the wattage and voltage of your water heater already, all you have to do is follow the Ampere formula, which is I (amps) = P (watts)/V (voltage) (volts).As an example, I have a 3,000-watt heater tank that requires 120-volt power to operate.You must divide your watts by the number of volts in order to obtain its amperage.Solution: P/V = I = P/V I is equal to 3000 watts x 120 volts.

I equals 25 amps.You could be thinking that a gadget with a current of 25 amps necessitates the use of a breaker with the same capacity.After all, it is at this point when overloading and over-tripping begin to occur.The National Electric Code (NEC) stipulates that you must maintain a continuous load of 125 percent of the maximum continuous load at all times.

In order to acquire the safe amount for your electric water heater breaker size, you must first complete this step.Applying the continuous load rule to the previous example, we get 31.25 amps: 125 percent x 25 amps = 31.25 amps.If this is the case, you can purchase the nearest amp size, which is 35 amps.The Square D by Schneider Electric HOM235CP is a highly recommended device for a 35-amp circuit breaker.If you have a 20-amp breaker devoted to your 25-amp water heater, you should anticipate the heater to trip the breaker on a regular basis.

  • Allowing enough room for your breaker will allow a power surge to occur without triggering the breaker.
  • Check out this video from House Wiring T.V.
  • to get a better understanding of how to properly size your water heater wires and breakers!

– Video on YouTube

What Size Breaker for 40 and 80-Gallon Water Heater?

Most households utilize a water heater with a tank capacity ranging from 40 to 80 gallons, depending on how much they rely on warm water on a daily basis.You’ll need their wattage and voltage to figure out how many amps breaker for water heater of these tank sizes you’ll require, and then you’ll use the answer from earlier.The typical capacity of a 40-gallon heater is 4500 Watts at 240 Volts, according to the manufacturer.Using the formula I = P/V once more, 4500W/240V Equals 18.75 amps.Then, taking into account the continuous load (125 percent x 18.75A), we’ll arrive at a total of 23.4 amps.

According to our response, a 40-gallon water heater requires at the very least a 25-amp breaker, which is the closest match to the amperage amount.However, I strongly advise utilizing 30-amp breakers because they are a more secure breaker size.For example, an 80-gallon heater fueled by 5500 watts and 240 volts will result in 5500W/240V x (1.25 continuous load) = 28.64 amps while operating at 5500W/240V.This means that a 30-amp dedicated circuit breaker is sufficient.

Pro-tip: Although a 30A breaker appears to be insufficient for an 80G tank, putting a 40A breaker will not safeguard the device in the event of an overloaded circuit.A breaker amperage that is far higher than necessary will not trip when it is required.

What’s the Correct Wire Size for a Water Heater?

  • If the wiring between a water heater and its breaker is mismatched, the connection will not function properly. Check that the amperage of your heater corresponds to the size of the wires on it. You can use the following list as a guide: 20-amp heaters require 12-gauge cable
  • 25-amp heaters require 10-gauge wire
  • 30/40-amp heaters require 8-gauge wire
  • and other big heaters up to 50-amps require 6-gauge wire.

Also, evaluate the size of your water heater’s circuit breaker. Circuit breakers rated at 30 amps, which are often used for big boiler tanks, require a 10-2 nonmetallic or MC cable. It is appropriate for starting loads up to 40 amps and a steady load up to 35 amps with this type of wire.

Preventive Measures Before Buying a Circuit Breaker

When selecting the appropriate water heater circuit breaker size, it is important to be mindful of the amp differential between the breaker and the water heater.It’s critical that you obtain the correct size.A breaker that is either too large or too little might result in an electrical hazard.If your circuit breaker is too tiny for the amperage needs of your water heater, you should anticipate your CB to trip on a regular basis.Not only that, but too much switching on and off of the heater might result in internal damage to the device.

It is not recommended that your water heater share a circuit with other appliances, and you should consider upgrading the circuit breaker if necessary.A breaker that is capable of handling a larger amperage than designed does not always imply that it is safer for the heater.If the tank experiences a sudden short circuit or overload, your circuit breaker will ignore the occurrence, providing no protection at all.


Choosing the appropriate size circuit breaker for a hot water heater is not that difficult if you obtain the necessary information.You can determine the right breaker size simply by studying the three wire heater factors — voltage, wattage, and wire size — and how they interact.A basic calculation would also suffice, but keep the breaker size as close as possible to the quantity of your response (the actual amp size of the heater).A 30-amp circuit breaker is commonly used for an electrical water heater, thus a circuit breaker such as the Q230 30-Amp Double Pole Type QP Circuit Breaker will be suitable for the job.

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