What Size Wire And Breaker For Tankless Water Heater?

What Size Breaker Do I Need for a Tankless Water Heater?

  • Has the question ″what size breaker do I require for a tankless water heater″ ever crossed your mind?
  • Knowing the right circuit breaker capacity may help you avoid electrical mishaps, ensuring that the structural integrity of your house and the safety of your family is maintained.
  • If you still have the tankless water heater’s user manual, determining the right breaker size for the tankless water heater is straightforward.
  • Still, don’t be concerned if you have misplaced this paper; I will assist you in determining the proper circuit breaker size for your tankless water heater.

What Size of Circuit Breaker Do You Need for an Electric Tankless Water Heater?

  • As previously stated, your tankless water heater comes with a user handbook that details the unit’s electrical needs, including the size of the hot water heater breaker advised for usage with it.
  • EcoSmart tankless water heaters, for example, need a single 30-amp breaker for each of its POU 3.5 and POU 6 tankless water heater models, although other versions, such as the ECO8, require two 40-amp breaker circuits.
  • Most Rinnai tankless water heaters, on the other hand, may be operated with a 20-amp circuit breaker.
  • You may also consult internet sites to determine the breaker size chart for your water heater based on the brand, model, and series number of your equipment.
  • In general, tankless water heaters require 40 amps to 50 amps for each wire, with the number of heating elements in the appliance equal to the number of wires.
  • Thus, if your water heater has three heating components, you may anticipate to utilize three cables and three circuit breakers to complete the installation.

If, for example, my tankless water heater requires 40 amps each wire, it adds up to a total of 120 amps for the tankless (40 amps x 3 wires or heating components = 120 amps in three 40-amp circuit breakers).

Can I Calculate the Correct Breaker Sizing for My Electric Tankless Water Heater?

  • When sizing a circuit breaker, electricians are required by the National Electric Code to take into consideration the electrical load in order to assure safety.
  • The rule of thumb is to double the amperage needs of appliances by 125 percent in order to calculate the proper size of water heater circuit breaker installation.
  • Your tankless water heater’s voltage and power ratings should be checked as soon as possible after purchasing it.
  • Consider the following scenario: your tankless water heater operates at 220 volts and 5,500 watts.
  • You must divide 5,500 watts by 220 volts in order to obtain 25 amperes in this situation.
  • Unfortunately, your calculations do not come to a close at this point.

You must also take into consideration the safety factor, which is mandated by the NEC.If you multiply 25 amperes by 125 percent (or 1.25), you will get 31.25 amperes as a result.As a result, a 35-amp breaker will be required for your tankless water heater.However, installing a 25-amp circuit breaker for the water heater in this scenario may result in the appliance being damaged as a result of the frequent tripping of the circuit breaker.

What Size Breaker Should I Get for a Gas-powered Tankless Water Heater?

A gas tankless water heater uses less electricity than an electric tankless water heater, hence it is more energy efficient. Generally speaking, a 120-volt dedicated circuit with a single-pole 15-amp circuit breaker is required for gas tankless water heaters. Regardless of the BTU rating of your gas tankless water heater, this is all you need to get it up and running.

Do I Have to Use the Correct Wire for a Tankless Water Heater Breaker?

  • When installing the electrical connections for your tankless water heater, it is also critical to use the proper electrical wire to avoid electrical shock.
  • For the connection between the tankless water heater and the circuit breaker, experts recommend using either a nonmetallic (NM) or a metal-clad (MC) electric wire.
  • MC cables are preferred by most electricians because they are more resistant to tearing, cutting, and other physical forces than other types of cables.
  • Non-metallic wires, on the other hand, are less difficult to handle and are less expensive.
  • When it comes to the electric wire gauge, it is preferable to consult the manufacturer’s recommendations for your tankless water heater.
  • As a general rule, the bigger the amperage or wattage rating, the larger the diameter of the electric wire should be.

Exceptions to this rule include: (the lower the gauge number).In the case of a tankless water heater with a 40-amp breaker, you may utilize an 8-gauge electric line, which is equivalent to 7.6 kW.A 6-gauge wire is required for an 11-kW appliance that is linked to a 60-amp breaker, on the other hand.

Do I Need a Separate Circuit Breaker for My Tankless Water Heater?

  • When it comes to tankless water heaters, many people wonder whether they need to install a separate circuit breaker for them.
  • Some homeowners believe that gas-powered tankless water heaters, which heat water using propane or natural gas, do not require electricity since they do not use energy to operate.
  • Tankless water heaters fueled by natural gas, on the other hand, feature electronic ignition systems, electronic thermostats, and a PC board.
  • Electricity is still required for the operation of these technologies.
  • You will be unable to heat water unless you have a sufficient supply of natural gas.
  • Similar to this, electric tankless water heaters are always powered by electricity to function properly.

Furthermore, in order to work securely and efficiently, these systems require a dedicated 240-volt circuit.Unlike traditional water heaters, tankless water heaters heat water on demand, requiring enormous quantities of electrical energy to be consumed in a short period of time.Electrical overloads become more likely if the tankless water heater shares its electrical power with other household appliances that are all connected to the same circuit breaker.It is critical to note that when on-demand water heaters are turned on and off, they might produce electrical surges or voltage changes in the surrounding area.

As a result, power-hungry and mission-critical appliances always require a separate or dedicated circuit breaker to be installed.As a matter of fact, it is an extremely important rule under the National Electric Code.


  • If you have the user handbook for your tankless water heater, answering the question ″What size breaker do I need for a tankless water heater?″ is simple.
  • If you don’t know what size breaker to use, you may figure it out by dividing the tankless water heater’s wattage rating by its voltage and multiplying the resulting number by 1.25.
  • An electric tankless water heater, on average, will require a 30-amp circuit breaker.
  • A gas-powered tankless water heater, on the other hand, will operate on a single-pole breaker rated at 15 amps.

What Water Heater Breaker Size Do I Need? (Electric Wiring Explained)

  • In general, electrical tankless water heaters require specialized electrical installation due to the fact that their load requirements are larger than those of other types of electrical equipment.
  • It is critical to have the proper type of breakers in place in order to avoid electric overloads and blackouts.
  • The following essay is intended for those who have pondered the topic, ″What water heater breaker size do I require?″

How is a Water Heater Breaker Measured? 

  • Amperes are the unit of measurement for water heater breakers.
  • Amperes are a unit of measurement for current, or the amount of electricity flowing through a circuit.
  • It is equal to the voltage of the circuit divided by the entire resistance of the circuit that represents the current.
  • It is necessary to have breakers in place in order to halt current flow when a malfunction in the electrical system is identified.
  • They must not only avoid harm, but they must also be able to handle a particular current without shutting down.
  • The average ampere consumption of a water heater is around 19.9 amps.

A tankless electric heater consumes around 100 to 120 amps to operate on its own.

Considerations When Sizing Breakers for a Water Heater 

Power Rating Of Your Heater 

The current drawn by your water heater system must be handled by circuit breakers. The greater the size of your tankless heater arrangement, the greater the amount of electricity your breakers must be able to manage. For the average water heater system, a 30 amp circuit breaker or greater is required.

Maximum current drawn 

You must ensure that your circuit breakers have enough capacity to manage the whole current flow. A 20-amp water heater, for example, requires a circuit breaker that is capable of handling at least 20 amps of electrical electricity. You must also ensure that your electrical system has been updated to supply the right quantity of current, or else it will not function correctly.

Current rating of your breaker 

Most homes are equipped with 15-20 amp circuit breakers, which are intended to withstand around 80 percent of their total amperage consumption. As a result, a 15 amp breaker can take approximately 12 amps while a 20 amp breaker can handle approximately 16 amps. Most likely, you will need to make changes to your home’s electrical system in order to draw additional power.

What Water Heater Breaker Size Do I Need? (How to Calculate) 

  • Calculating the appropriate breaker size for your heater is a pretty simple process.
  • You must first determine the machine’s power rating (measured in watts or kilowatts) as well as the voltage that it requires.
  • Because current is just the product of power divided by voltage, you may calculate the magnitude of the breaker current necessary for your heater by dividing these two values in half.
  • Consider the following scenario: you have a normal 1,500-watt water heater that operates on a 120-volt system.
  • 1,500 divided by 120 equals 12.5, which means you’ll need at least 12.5 amps of current to get the item running.
  • Most breakers, on the other hand, are intended to operate at just 80 percent of their maximum load capacity.

Consequently, to meet our 12.5 amp current needs, we would want breakers that could withstand at least 15 amps of power.In an ideal situation, you should be able to identify breakers that can manage at least 125 percent of the demands of your water heaters.On a 120-volt circuit, a 50-gallon tank consumes around 4,500 watts of electricity.Using the arithmetic, that works out to around 37.5 amps in total.

According to the 125 percent guideline, we require breakers that have a minimum capacity of 47 amps.As a result, seek for breakers that can handle 40-50 amp loads.

Water Heater Breaker Size Chart 

The following table indicates the sizes of circuit breakers and copper wire that are necessary for tankless water heater units. Please keep in mind that these are only educated guesses. Always be sure that you are following the exact directions provided in your user’s handbook.

People also Ask (FAQs)

Can I replace a 30 amp breaker with a 60 amp breaker? 

This is only possible if you also replace the cable with one that can handle the additional current. A fire might occur if you simply switch the 30 amp breaker out for a 60 amp breaker without additionally altering the wires in the circuit.

What size wire should you use for a 60 amp breaker? 

To safely operate a 60 amp breaker without the risk of damaging it, you must use at least a 6 gauge (4.1mm) wire; the higher the current, the thicker the wire you must use.

Can I use a 40 amp breaker for a water heater?

Yes, it is possible to utilize a 40 amp breaker for some water heaters. Some tankless electric water heater units may be powered by 40 amp circuit breakers as well.

How many amps can a 30 amp breaker handle? 

A 30 amp breaker is capable of handling currents of up to 30 amps, although it is only suggested for usage at voltages of about 25-26. Generally speaking, a breaker should only be utilized at around 80% of its maximum amperage rating.


Electric hot water heaters consume significantly more electricity than other equipment, therefore you must ensure that you have the appropriate circuit breakers and cables installed. As a result, be certain that your water heater system is equipped with the appropriate breakers.

What size wire is needed for electric water heater?

  • Current and wire gauge sizes that are commonly used Installing a hot water heater requires the use of wire that is large enough to handle the current demand of the heater.
  • Typical hot water heater sizes are as follows: a 20-amp hot water heater requires 12-gauge wire, a 25-amp hot water heater requires 10-gauge wire, and a 30- to 40-amp hot water heater requires 8-gauge wire.
  • Electric hot water heaters normally need the installation of a dedicated 30-amp, 240-volt circuit breaker.
  • The 10/2 Romex cable that runs from the breaker panel to your water heater is often used to deliver electricity to your water heater (Blk wire- hot, Marked White wire – hot, Bare copper wire – ground).
  • In the same vein, what size wire do I want for a water heater that consumes 4500 Watts?
  • In order to power a 4500-watt element, 10/2 wire and a 30 amp (220volt) breaker are required.

The 3800 may be connected with 12/2 wire and a 20 amp breaker, depending on your needs.In light of this, what gauge of wire do I require for a 50-gallon hot water heater?In order to accommodate a water heater, the usual circuit configuration is 10 conductors with ground (10/2), with a 30 amp circuit breaker for the water heater.If you’re going to run cable anyhow, simply run 10 and replace the breaker to make sure it’s done correctly the first time.

Approximately how many amps does a 50-gallon water heater consume?The majority of 50 amp water heaters will have components that are 4500 watts.No, a 20 amp circuit breaker will not trip if the load is 4500 / 240 = 18.75 amps, but it will be working at over 95% of its 20 amp capacity, and most circuit breakers are not rated to handle that much current.

What Size Breaker for Electric Tankless Water Heater?

  • Isn’t it frustrating and time-consuming when you buy a breaker and an appliance, only to discover that they don’t work together?
  • It can be difficult and time-consuming to figure out what size circuit breaker to utilize for an Electric Tankless Water Heater (ETWH) at times.
  • It’s also time-consuming because you’ll have to purchase a circuit breaker for each terminal/heating element you use.
  • So, in order to determine the appropriate breaker size, you must first determine the wattage, voltage, and amps of your water heater.

Picking the Perfect Breaker Size

1. Refer to the manual

  • Now, the most dependable and precise approach for determining the proper breaker size for a water heater is to consult the instructions that came with your electric tankless water heater.
  • In addition, you can see the sort of wiring that it has, which is comparable to the amount of breakers that are required for the equipment in question.
  • Is it a 3 x 50 (which implies that there are three heating elements protected by three 50-amp circuit breakers) or a 4 x 40 (which means that there are four 40-amp circuit breakers) circuit breaker?
  • It is always dependent on the model that you are using.
  • Keep in mind that the more the number of breakers and the higher the amperage they provide, the greater the electrical current.
  • Electric tankless heaters may draw currents ranging from 42 amps to 167 amps at their maximum capacity.
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If, on the other hand, you are unable to locate the manufacturer’s instructions, you may always resort to the mathematician’s technique.

2. Use the Power formula

  • Make use of the power equation, P= I x V, from which we may get the following formula to determine the amp size: I= P x V (where I equals amps, P equals watts, and V equals Volts).
  • Because the normal voltage for an ETWH is already 240 Volts, you’ll just need to determine the amount of power input or watts required by your device, which may be found on the device’s specifications sheet or on the water heater itself, to complete your installation.
  • Following the collection of all of the necessary factors for a tankless water heater breaker size, you may proceed to the calculation.
  • Allow me to give you an illustration.
  • Consider the following scenario: a heating element requires 7600 watts from a 240-Volt circuit.
  • To get the amperage, divide 7,600W by 240V as follows: I = 7,600 watts 240 volts I = 7,600 watts I = 31.7 volts/amps Ultimately, it is determined that 31.7 amps are necessary in order for this heating element to function properly.

Although it is possible to use the precise amperage as the breaker size, doing so is not recommended.When installing a tankless water heater, do not utilize the same calculated amperage as your final size breaker.If you don’t do this, you run the danger of having an accident since there will be no protection against a power surge.An electrical circuit breaker should only be capable of handling 80 percent or less of its overall capacity, according to the National Electric Code (NEC).

This safety measure is required because 100 percent continuous loads create heat that is potentially harmful enough to spark a fire at the circuit breaker’s wire connections.We’ll go with the previous example, which is 31.7 amps.To get the breaker size, multiply 1.25, or 125 percent, by the rated amp of your device, which in this example is 31.7 amps, to obtain the breaker size.CB Size = 125 percent multiplied by 31.7 equals 39.62 Amps Finally, depending on the final result (39.62 amps), purchase the breaker that is the closest in size.For example, for a safe maximum continuous load on our sample heating element, the breaker you should purchase is 40 amps.

Take notice that in this scenario, there was just one circuit breaker for a single heating element to consider.Some water heaters have numerous heating elements, as I previously said, necessitating the use of multiple circuit breakers for each heating element.Take into consideration various heating components, as well as the main heating element.

Electric Tankless Water Heater: How It Works

In addition to the electric water heater breaker size, you may be interested in learning more about how this machine operates, its advantages and disadvantages, and its total power.If you have an old tank water heater, you may already be familiar with the mechanics of a water heater.Tankless and traditional water heaters are not that dissimilar in terms of performance, but there is a significant difference in the amount of electricity they consume.In contrast to conventional heaters, which contain the hot water within as it boils, the ETWH uses electrical components to heat the water that is contained inside the pipelines.These elements use energy and are protected by several breakers (one breaker for each element) rated 40-50 amps, which are distributed throughout the system (the typical rating).

  • Different manufacturers provide extras and premium features in each ETWH that they produce under their own brand.
  • Every product, on the other hand, is based on the same premise.
  • It is straightforward.

A faucet is opened, and the heating element is activated as soon as the flow of water is detected by the gadget.Once the flow is stopped, the heat elements also come to a halt in their functions.The size of the breaker for an electric water heater is always determined by the amount of electricity that will be supplied and the voltage that will be necessary for the heater to operate.The wattage of the heater (which can range between 10 kW and 40 kW) can be found in the handbook.An additional point to mention is that an electric tankless heater takes its power from a 240 Volt circuit.

Many people opt for this type of heater because it provides them with the convenience of having an endless supply of hot water.Other advantages include immediate hot water, space savings, long-term durability, and affordable monthly expenses for tiny residential houses with limited space.On the other side, there are disadvantages such as the need for additional equipment, the high cost of maintenance, and the inconsistency of water temperatures.

Is Your Main Breaker Panel Suitable for Your Water Heater

Electric tankless water heater installation requirements include a large main breaker panel for safety reasons, as a result of the several circuit breakers supplying each heating element.So, before you go out and buy a whole new heating equipment, ask yourself: ″Do I really need to change my panelboard?″ Given the rapid advancement of technology in recent years, 100-amp panels are enough for powering major appliances such as dishwashers and air conditioners.The most recent ETWH available today is incapable of operating at so low an amp.You could wonder how and why this is happening.Assume you have three breakers rated at 40-50 amps each, each of which is powering three heating components.

  • When you add it all together, that’s already 120+ amps, rendering your 100A panel completely ineffective when an ETWH arrives.
  • 125 percent of the heater’s continuous load might be calculated to determine the size of your primary breaker panel if you do not know how to do so.
  • As an illustration, let’s look at our Power formula once more.

It is important to note that electric tankless boilers can consume anywhere from 10,000 to 40,000 watts.We’ll use 30,000 Watts as a practical example of a domestic ETWH to illustrate the concept.Therefore: I= 30,000 watts at 240 volts 125 Amps is the value of I.Continuous load = 125 percent x 125A = 156.25 Amps Continuous load = 125 percent x 125A If your heating unit requires this amount of amps, the ideal panelboard to use is the biggest available, which is 200 amps in size.It is important to note that a standard 200-amp breaker panel should not be able to manage more than 160 amps at a time.

To be safe, it’s important to talk with your reputable contractor and have him examine the total power input of your ETWH and other electrical equipment before making any decisions.After that, you’ll be able to determine the optimal panel size.


When it comes to determining what size breaker to utilize for an electric tankless water heater, responsibility and meticulous calculations play a significant role.Before you install this heating device, you should pay close attention to the size of your fail-safe device or devices, which will protect your home from electrical and fire accidents in the event of an electrical or fire disaster.The best course of action is to consult with a licensed electrician to identify the most appropriate breaker amp size.If you intend to do it yourself, however, the Power formula, which is a straightforward mathematical procedure, should be followed: calculate the amperage by dividing the wattage by the voltage.Last but not least, determine the continuous load by multiplying 125 percent by the final amperage received.

What size breaker do you need for a tankless water heater?

120 volts at 120 amps Furthermore, does a tankless water heater necessitate the installation of a dedicated circuit?A tankless water heater will need the installation of a dedicated circuit, which will be stated in the installation manual of the unit that has been chosen.Quad circuit breakers may be permitted in the panel if there is insufficient room for the circuit breakers in the panel, depending on the make and type of the panel in question.In a similar vein, one would wonder, ″What size circuit breaker do I need for a 220 volt water heater?″ 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.

  • What size circuit breaker do I need to connect a 240 volt water heater to my home?
  • Considering that the load is entirely resistant, 5500 watts at 240 voltage is 23 amps; thus, the breaker is designed to handle 30 amps and the wire is 10 awg.
  • 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 Tankless Water Heater?

A gas tankless water heater only requires a dedicated single-pole breaker with a 15-amp, 120-volt rating for this reason.

How many amps do you need for a tankless water heater?

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.

Why do tankless water heaters need 3 breakers?

The average electric tankless water heater, on the other hand, requires at least 120 amps to run, but the average household’s total capacity is 200 amps. 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.

What breaker does a tankless water heater use?

What size breaker and cable do I need for a tankless water heater? No section of a single wire can be separated in order to connect to numerous terminals. Tankless systems typically require a 40-50 amp breaker for per wire.

Is 150 amp service enough for tankless water heater?

Typically, tankless heaters do not work effectively on services with currents less than 200A, and in many circumstances, an upgrade to a 320A service is required.

Does a tankless gas water heater need a dedicated circuit?

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.

Does a tankless water heater need a GFCI breaker?

GFCI protection is required in a garage for every 120, 15 and 20 Amp receptacle outlet, which means that if you install a tankless water heater in the garage, it should also be protected by this standard.

What is the downside of an electric tankless water heater?

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.

Do I need an electrician to install a tankless water heater?

Installation of a Tempra tankless water heater by Stiebel Eltron. A tankless water heater installation is NOT considered a ″do it yourself″ job in the traditional sense. An electric tankless water heater such as the Stiebel Eltron is reasonably straightforward to install and may be completed by any qualified plumber and electrician.

What size wire should I use for a 30 amp breaker?

THUMB RULES AND REGULATIONS These are the rules of thumb that many techs will repeat over and over again and rely on in all situations: ″Twelve-gauge wire is good for 20 amps, 10-gauge wire is good for 30 amps, 8-gauge is good for 40 amps, and 6-gauge is good for 55 amps,″ and ″The circuit breakers or fuses are always sized in order to protect the conductor.″

Do tankless water heaters use 220 volts?

If you intend to acquire an electric tankless water heater, you should be aware of the following electrical specifications: Voltage – Many merchants sell devices that can support voltages ranging from 110V to 277V, including 110V, 120V, 208V, 220V, 240V, and 277V. Amperage – The amount of electricity required by different electric water heaters will vary significantly.

What size breaker do I need for a Rheem tankless water heater?

The unit requires a dedicated 40 AMP breaker and is 10 inches high by 7-1/4 inches wide by 3-1/4 inches deep. Hot water in less time!

Does a water heater have its own breaker?

Electrical Consumption A breaker is required for every hot water heater, whether it is gas or electric, that has an electrical connection…. It is wired to a separate circuit breaker in this scenario, in line with the National Electrical Code, article 220-30 for new construction and article 220-31 for existing structures, as specified by the National Electrical Code.

How many amps does a 80 gallon water heater pull?

A water heater will only draw the amount of electricity required by the wattage of the element (s). As a result, your WH is equipped with two 4500 watt elements. It draws around 22 amps when only one is running (208 is nominal voltage, which is what you have in your building) 4500/208= 21.6 amps when only one is running.

How many amps does a 40 gallon water heater use?

When wiring a 16amp heater, it is recommended that a 20amp circuit be used and protected by a 20amp circuit breaker, rather than a 20amp circuit being used and protected by a 20amp circuit. If a 2500w heater is connected to 240v, it will consume 2500/240 or 18.75 Amps and either 25 or 30 Amps, depending on the code.

Does a tankless water heater work if the power goes out?

Even though on-demand gas water heaters do not use electricity as a fuel source to heat water, on-demand heaters typically feature a control panel that is powered by electricity, which serves as the water heater’s ″brains.″ Therefore, even a tankless gas water heater will not function independently in the event of a power failure.

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How to Wire a Tankless Water Heater – Complete Guide

How to Wire a Tankless Water Heater in 2022 is an important issue to ask since no tankless water heater can function without electricity in the year 2022.This is due to the fact that each tankless water heater is equipped with an internal PC circuit that regulates the machine.A portion of it may be seen on the tankless water heater’s display screen, which is visible in black and white.It might be beneficial to know a few things about wiring or to have a thorough grasp of it in order to diagnose and install a new tankless water heater.We do not, however, recommend that you do so on a consistent basis at all times.

  • Because there are various factors to consider that can make or break your decision to purchase a tankless water heater, it is important to do your research.
  • So, in order to avoid any difficulties that may arise as a result of carelessness, make sure to read the full article.
  • We are all aware that installing a tankless water heater is an expensive endeavor, and most of us would prefer to save money whenever possible.

If you are unsure of how to wire a tankless water heater, the following information may be helpful.A licensed expert, however, is recommended by the majority of tankless water heater manufacturers to complete this task for you.This is due to the fact that a professional is fully conversant with the specs and functionality of installing a tankless water heater.A brief explanation of tankless water heaters is provided below, followed by information on wiring a tankless water heater to a home electrical system.It is intended for individuals who are interested in a tankless water heater but do not wish to purchase or install one themselves.

When it comes to tankless water heaters, they’re also referred to as on-demand water heaters and, on occasion, as instant water heaters.They are not like a standard water heater in that they do not store water in a tank or heat water on a regular basis.However, what they do is heat water at the precise moment you want it, whenever you require it.Because they only heat for a certain period of time, the amount of energy consumed is similarly restricted to that period of time.

  1. You will be able to see a significant amount of savings as a result of energy efficiency in this manner.
  2. Furthermore, before making a decision on which tankless water heater to purchase, you should consider some of the features that are available.
  3. A tankless water heater should be evaluated based on the following characteristics: What kind of gasoline does it operate on?
  4. (Natural Gas, Propane, or Electricity) Unit that may be used indoors or outdoors The cost of the initial installation plus any additional costs Efficiencies in energy use or The Energy Factor is a factor that determines how much energy is produced.
  5. Flow Rate (also known as Capacity for Heating Water to the Maximum Knowing and understanding these factors is essential if you want to make educated selections.
  1. Returning to our subject, you should be aware with the many types of tankless water heaters available on the market.
  2. It is necessary since the wiring technique varies to a certain extent depending on the kind of wiring.

Tankless water heater types:

Tankless water heaters may be divided into two types: on-demand and tankless. The engine is powered by gas. Operated by electricity

Gas operated water heaters:

These units are powered by the combustion of natural gas or propane, which is obtained from the surrounding environment.As a result, you must deal with the hazardous gases that are produced during the combustion of gases.As a result, suitable vents must be put on such a water heater in order to exhaust the gases outside your home.It is not necessary to build vents if the unit is positioned outside.The fact that gas tankless water heaters are largely fueled by natural gas or propane means that they require just a little amount of electricity to run the PC circuit or display screen.

  • Because of this, a 120-Volt circuit is required for its operation.

Electric operated water heaters:

Electric tankless water heaters operate on electricity rather than natural gas or propane to provide power for their operations.As a result, they do not require an exhaust vent to discharge outside the home.Despite the fact that they are electric tankless units, they have more stringent electrical requirements for your home’s electrical circuit.Electric water heaters require 240-volt electricity to operate.Furthermore, because of their incapacity to meet significant demands, they are most suitable for small homes (providing hot water to 4-5 faucets at the same time).

  • This article goes through the process of wiring an electric tankless water heater in great detail.
  • A gas tankless water heater necessitates the construction of additional gas pipelines and vents, among other things, that have nothing to do with the wiring procedure.

Requirements for wiring a tankless water heater:

Before a tankless water heater may be built, it is necessary to meet the requirements listed above.

Checking Warranty:

Some tankless suppliers include a condition in their warranty that requires qualified professionals to do the installation. If you choose to install the tankless unit yourself, the warranty on the tankless unit may be voided as a result. As a result, making an effort to save money may result in a more significant financial loss.


Prior to installing these water heaters in your home, you may be needed to get a permission or license from the appropriate authority in your state. These water heaters are also subjected to inspection and testing by regulatory agencies to ensure that all standards, specifications, and operational characteristics are met.

Electrical circuit requirement:

When installing a Tankless Water Heater in your house, it is recommended that you have a 240 Volt circuit installed.

Tools Required:

After that, we’ll go into what tools will be required for you to properly wire your tankless water heater.The following is a list of the most important tools for your convenience.Machine to drill holes in the ground Drill bits for use with a drilling machine a screwdriver with a round head Adjustable Wrench with a crescent shape a flathead screwdriver is a screwdriver with a flat head.Pliers with a needle nose are sometimes known as needle nose pliers.A measuring tape is a piece of tape that is used to measure something.

  • Pipe cutters are a type of pipe cutter.
  • Pencil

Skill required:

Having some tools does not imply that you are capable of performing a task like an expert.In order to complete the assignment, you must have adequate talents to match the tools available.These are the abilities required for the wiring of a tankless water heater.To work with electric appliances, you must have intermediate or advanced level understanding of electricity and how to operate electric equipment.Additionally, it would be great if you were a Licensed Electrician or hired an expert to do the installation to ensure that there are no problems.

How to Wire a Tankless Water Heater:

When installing a tankless water heater, it is important to keep the following factors in mind: Always photograph each stage before making any changes to ensure that you can easily restore the prior setup if necessary.An ideal location for a water heater is adjacent to a supply of hot water that is often used by your household.You’ll get hot water much more quickly if you do it this way.It is important to remember to place the tankless electric water heater upright, with the electrical and water lines facing downward.Furthermore, it should be located in an area that is sufficiently open so that you may do maintenance.

  • Typically, this is a location where you may have access to electrical outlets and the sewage drain.
  • A common rule of thumb is to avoid locations where there is a lot of traffic.
  • There is a high likelihood of liquid splashing over your water heater in this situation.

When there is a reasonable risk that temperatures may fall below freezing point.In areas where there is an excessive amount of moisture or humidity.

Removing your Old Water Heater:

Tank water heaters are relatively simple to install, and they can be easily replaced by just removing them from the tank. A great deal of scientific or technical expertise is not required. It becomes considerably simpler if you follow the steps in a sequential manner. To finish the procedure, simply follow the instructions outlined in the following section.

1.  Disconnecting the power:

No matter what type of electrical device you are working with, you should never attempt to disassemble it while the power is still on.It is possible to get shocked, which might be life-threatening.As a result, the first step is to turn off the electricity to the appliance.You may accomplish this by shutting off the breakers, which will interrupt the flow of electricity.Check it again with a voltage tester or a voltage meter to confirm there is no voltage present in the unit.

  • If the water heater is powered by natural gas, turn off the gas supply.

2. Pressure valve and Drain valve

Release the pressure valve in the tank, but make sure to put on your safety gear before doing so.Because of the high pressure, hot water may splatter on you if you don’t put on your gloves and safety eyewear before starting.Take extreme caution.After releasing the pressure in the tank water heater, remove the remaining water in the tank to prevent overflowing.Also, make sure that the water supply valves are stopped so that freshwater does not continue to be pumped into the system.

  • 3.
  • Remove the lid from the junction box: On the top of the tank water heater, there is often a junction box for connecting various components.
  • Wires may be seen running into a compartment that is covered with metal plates.

The metal plates can be removed by using a screwdriver or a drill machine to bore holes in them.By removing the lid, you will be able to access the wire connection point with the water heater.You may, however, require the use of a needle tip plier in order to detach the connections.Using an adjustable crescent wrench, undo the pipe connections and then carefully lift the tank water heater off of its mounting brackets.

How to Install a Tankless Water Heater:

  1. Location selection and mounting

The first step in the installation procedure is determining where the tankless unit will be placed in the home or business.Make ensure that you have taken into mind all of the tankless factors listed above.Once the location has been determined, the device should be mounted to the wall.Because most tankless water heaters are designed to be wall-mounted, you should have no trouble installing one if you follow the instructions in the handbook.The procedure, on the other hand, may vary depending on the brand and model.

  • Tankless water heaters are delivered with screws and anchors that you may use to drill holes in the wall, and the tankless unit is put on top of them for further stability.
  • 2.
  • Connect the tankless water heater’s pipes (water and gas) to the house.

Make sure that all supply lines are turned off before connecting the pipe to the tankless water heater.This is necessary since new circumcisions will need to be created in order to guide the new pipes away from the current pipelines.It is also an opportune moment to make a move.As of right now, you may make a variety of installations that will help you to extend the life of your tankless water heater significantly.Installations such as insulating valves and a pressure release valve are required in some cases, while others are optional.

At the same time, additional beneficial installations such as a lowering valve are available (which you can install if the water pressure coming to your home exceed 150 psi).Additionally, a water softening system (which you may install if your neighborhood has hard water) is recommended.It can assist in reducing the accumulation of scale and silt in the tankless unit).3.

  1. Putting the pipes together Once the pipes have reached the tankless unit, the process of attaching the pipes differs depending on the type of pipes you’re working with.
  2. A standard fitting using a wrench or a mix of rubbish and cement will suffice in most cases.
  3. Additionally, be sure to put Teflon tape or plumbers tape between the connecting points of the pipes to guarantee that there are no leaks.
  4. Teflon tape is an excellent choice for sealing any gaps that may exist between the fittings.
  5. One thing to keep in mind is that you should never permanently solder the pipes together.
  1. Because you may need to detach them for repair or any other reason in the future.
  2. 4.
  3. Connecting the tankless water heater to the electrical system The front panel of the tankless water heater must be removed in order to have access to the wiring.

You’ll see that the device has a significant quantity of cable in its construction.Be certain that you will not be dealing with a large number of them.Every wire within the device has previously been identified and categorized.All that is required is the wiring of the connections between the circuit and the tankless water heater.Due to this, it is necessary to take into account two different aspects.

What size wire should you use, and how many breakers should you use, are all important considerations.Following the directions in the tankless water heater’s instruction manual will provide you with the most accurate information on how to accomplish this.Among the other factors to keep in mind are the following: The quantity of specialized circuitry required will be specified in the installation instructions for the equipment you now own.

Depending on the make and type of the panel, you may be able to utilize a quad circuit breaker if you want extra space for the circuit breaker in the panel itself.Assume that your electrical panel has the capability of supporting the usage of twin or tandem breakers.Then you may replace the old full-size circuit breakers with twin circuit breakers, which will free up room for the installation of a new circuit.This is only applicable if your electrical panel has the option of having twin or tandem breakers.

After that, double-check the connections and put the front panel back in its original position.Make sure that the water supply is turned on and that the water is allowed to flow through the unit before checking for leaks.Switch on the power after everything is in working order and enjoy your tankless experience.Time required is estimated to be: The installation of a tankless water heater takes between one and five hours by a qualified technician.A novice, on the other hand, will take far longer to do this task.

Because the amount of time required varies depending on the amount of experience and familiarity with the task.


You must make certain that any electrical wire connections to, from, or inside the tankless water heater are securely fastened in place.Additionally, instead of sloppy wiring connections, it is necessary to keep the wirings neat and tidy.As a result, it may be difficult to determine which wire is responsible for which function if you have any issues in the future.It is preferable if you adhere to all applicable electrical and plumbing rules and obtain approval from the appropriate authorities.Obtaining approval from the appropriate authorities is necessary because you need to determine whether or not your local transformer can sustain the circuit expansion.

  • In the event that it was unable to support the upgrade and hence ceases to function.
  • You may be required to pay a charge to the authorities in order to obtain a new transformer.
  • So it is strongly advised that homeowners refrain from performing any electrical circuit or panel repairs unless they are professional electricians.
See also:  How To Check Heating Element In Water Heater

Frequently Asked Questions

In order to use a tankless water heater, what electrical criteria must be met?Electric tankless water is a high-power gadget that requires a minimum amperage of 120 to function properly.In comparison, the majority of residences have an electrical circuit with a capacity of 200 AMP.As a result, the existing electrical circuits are unable to fulfill the demands of the electric tankless water heater.- As a result, you will need to update it.

  • Is there an unique wiring need for tankless water heaters?
  • For your tankless water heater, you must utilize 8-gauge wires, which are an updated version of the wires that are currently in use in your electrical circuit.
  • It is possible that the electric line that was used for your prior water heater will not cut while giving enough energy to the tankless unit.

What is the minimum number of wires required for a tankless water heater?The number of wires required by a tankless water heater is determined by the number of heating components in the unit.In a similar vein, you should add 40-50 Amp breakers for each line to guarantee that your tankless unit lasts for the maximum amount of time possible.


Know-how on how to wire a tankless water heater in 2022 will be beneficial whether you are installing the tankless water heater or diagnosing any problems that may arise from it.Saving money is a prudent course of action.However, this is not always the case.As a result, you must determine if your tankless supplier permits do-it-yourself installation or whether they need installations by a licensed expert.Some tankless manufacturers include a condition in their warranties that specifies that professional fittings must be used.

  • This implies that, despite being less expensive, a do-it-yourself installation may end up costing you a significantly larger money in the form of voiding your warranty.

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:

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.

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!

  1. – 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.

Wire Size For Water Heater Based Upon Amp, Watt, Gallon

Do you have a brand-new water heater in your home? Are you considering doing the electrical work yourself? You’ll need cables that are the proper size. A fire might be started if the improper size is used.

What Size Wire Do I Need For My Hot Water Heater?

When it comes to amperage, When it comes to wattage, For a tankless water heater, the gallon wire size is important. The thicker the wire is, the higher the amp rating of the circuit. This is the approach taken by the majority of electrical experts. Once the water heater’s amp rating surpasses 50A, they will only utilize 6-gauge wire to connect it.

How Do I Find Out What Size Wire Is Best For My Water Heater?

The amperage is required in order to compute the correct wire size.Consider the following scenario: you have a 3,000W heater that operates on 120V.Following the 80 percent rule, the amperage is calculated as (3000/120)*80 percent, which results in a total of 45 amps.According to the amperage table, 8 gauge wire is the ideal wire size for a 3000W heater.You must also take these considerations into consideration.

1). Voltage

The majority of water heaters operate at 220-250V. They make use of a two-circuit breakers. Because the volta

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