Electric tankless heaters rely only on electricity to warm up the water in their tanks.
As is common knowledge, heating water is a relatively labor-intensive process.
Because of this, electric tankless water heaters need for a substantial amount of amps, which stands for amperes.
How many amps are needed to power a tankless water heater?
The amount of current that tankless heaters require may range anywhere from 42 to 167 amps.
Because of these two crucial parameters, we are able to compute the precise number of amps that are required by a tankless water heater:
- Total power, often known as watts. Electric tankless water heaters have a power intake that ranges anywhere from 10,000 watts to 40,000 watts (40 kW).
- Voltage. Every electric tankless water heater runs on a 240-volt circuit so that the current draw may be kept to a minimum.
Using the equation for electric power, which is P = IV, we are able to compute the by expressing the I, also known as the electric current, as follows:
I (amps) = P (watts) / V (volts)
Example: Consider the following scenario: we have a tankless water heater with 240 volts and 30 kW of power.
How many amps does a tankless water heater with 30 kW need to operate? The following is an example of how we apply the electrical power equation:
I (amps) = 30,000W / 240V = 125 amps
This kind of heater uses 125 amps of electricity (you need several 20-amp or 30-amp breakers for installation).
The results of our calculations for the amp draws of tankless water heaters with capacities ranging from 10 kW to 40 kW are presented in the table below:
How Many Amps Do Electric Tankless Water Heaters That Range From 10-40 kW Draw?
For the sake of all of these calculations, we will assume that the heater is connected to a circuit that operates at 240 volts.
| 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 |
With the help of this amp draw chart, you will be able to make an exact estimation of the number of amps that your tankless hot water heater uses.
After that, you will be able to make a decision on the quantity of amp breakers that will be required for the installation.
You may see our ranked list of the top tankless units here if you are interested in purchasing a tankless water heater in the near future.
