How Many Amps Does A Tankless Water Heater Use? | Home Improvement 2022

Over the past few years, tankless water heaters have garnered a lot of hype, all because of their knack to deliver you a limitless amount of seamlessly warm water. 

Nonetheless, simultaneously, you must know the requisites, including how many amps does a tankless water heater use to ensure you don’t overload your residence’s existing electrical system. 

An electric unit requires a minimum of 120 amps to work, and the average residence’s total capacity is 200 amps. 

It means you will certainly have to upgrade your residence’s electrical system to support a larger power load demand. 

Additionally, it will also need a large and pricier motor loop and main panel for the property. 

However, the exact amount of how many amps does a hot water heater pull depends on various factors such as heater type, fuel type, energy efficiency, and capacity. 

Though, occasionally, you as a customer might have to pay for the wiring between your meter and community electricity supply transformer. 

How Many Amps Does A Tankless Water Heater Use

Now, you might be thinking that how can I figure out whether my residence’s power system needs to be exalted or not, right? 

Well, the best thing you can do is to employ a professional technician and acquire his opinion about your electric system to avoid any last-minute disaster. 

If you plan to switch from your traditional tank-style water heater to a tankless machine in your older house, then the deployment expenditures will be much higher than they would have been if you had deployed the tankless appliance in a modern property.

How Many Amps Does A Tankless Water Heater Use?

Instant water heaters need around 42 to 167 amps. However, an average device requires 120 amps to work proficiently, which is much higher than the standard heaters that demand only 30 amps to run. 

Old-fashioned properties have 100 to 120 amps, so they will unquestionably require an upgrade in the electrical system. 

Only an expert technician should perform this upgrade. He may have to add circuit breakers’ subpanel to your residence to boost the total amount of amps available. 

Besides, their breaker size and wire gauge should meet your area’s state, provincial, local, and national electrical codes. 

Subpanel deployment is also critical for these devices, especially if you are not installing the unit within the view of the primary electrical panel.

Also, the wiring should be sturdy enough to maintain the voltage drop of less than 3 percent under load. 

You might feel that the initial investment is extremely high, but you must understand that on-demand heaters are highly energy smart. 

Modern models are up to 94% energy efficient. If you have several electrical appliances at home, you will need an extensive power system than you currently have. 

It does not mean that electric machines are not a good option. You will need to upgrade your electrical system.

On the other hand, the whole house tankless appliance with 28,000 watts will need a wire and circuit breaker that will accommodate 120 amps at a much higher cost than an electrical system to a tank-style unit. A traditional unit with 4500 watts needs 30 amps and #10 wire. 

Now, you may be wondering how many amps does a gas tankless water heater use. Well, if you have a gas heater, first take into account your ventilation needs and examine your existing gas line. Some brands provide gas emission kits that you can buy for proper installation. 

When it comes to amps, gasless machines need only minimal electrical connections. You must check the installation demands of the model at the time of purchase.

How Many Amps Does A Hot Water Heater Draw

How Many Amps Does A Hot Water Heater Draw?

Tankless Heater Size (In kW)Electrical Current (In Amps)
10 kW42 Amps
11 kW46 Amps
12 kW50 Amps
13 kW54 Amps
14 kW58 Amps
15 kW63 Amps
16 kW67 Amps
17 kW71 Amps
18 kW75 Amps
19 kW79 Amps
20 kW83 Amps
21 kW88 Amps
22 kW92 Amps
23 kW96 Amps
24 kW100 Amps
25 kW104 Amps
26 kW108 Amps
27 kW113 Amps
28 kW117 Amps
29 kW121 Amps
30 kW125 Amps
31 kW129 Amps
32 kW133 Amps
33 kW138 Amps
34 kW142 Amps
35 kW146 Amps
36 kW150 Amps
37 kW154 Amps
38 kW158 Amps
39 kW163 Amps
40 kW167 Amps

This table can help you precisely evaluate how many amps do you need for a tankless water heater and what size breaker for electric tankless water heater is required for installation.

Frequently Asked Questions

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

They need at least 120 amps to function properly, and the capacity of an older house is 200 amps. So, it is essential to upgrade the electrical system to support the hefty load demand, which could cost approximately $1500.  

Q. What Size Breaker For Electric Tankless Water Heater?

They need a 40 to 50 amp breaker for each wire. 

Q. Do Instant Water Heaters Need A Dedicated Breaker?

Yes, you will have to add 3 circuit breakers to the interior panel and pull three new circuits. Many residences don’t have 3 open spaces in the panel to make the heater installation possible. 

Q. Do Electric Water Heaters Require 220 Volts?

Many electric units work on 220 to 250 volts. This voltage needs a double circuit breaker evaluated for the amp draw of the devices.


In this era, having warm water is not only an amenity but a necessity. Therefore, you need to procure a model that meets your requirements and fits your budget—both initial expenses and daily usage. 
Also, you must determine the overall amount of energy your water heating system will utilize from your residence to assure your current electrical service can handle the demand. 
We hope you liked our article on “how many amps does a tankless water heater use.” If yes, please share this piece of information with those who need it.

Similar Posts