The amperage on such a tank is i w e.
Electric hot water heater amp draw.
A 20 amp breaker would still be large enough.
You have stated that the calculated amperage load for 4500watt at 240volts is 18 75amps however nec article 422 13 states that the minimum circuit rating for a water heater must be 125 of the rated load so this 4500watt load requires a minimum circuit of 23 44 amps at 240volts.
In a us household the current draw for a 1500 watt water heater is 12 5 amps.
Unfortunately the average electric tankless water heater needs at least 120 amps to operate and the average household s total capacity is 200 amps.
For example if the heater operates on the same circuit as four continuously running 60 watt lightbulbs you need to add 2 amps to the total current draw.
This means you will have to upgrade your electrical system to accommodate for the larger load demand which could cost you up to 1 500.
The ge water heater se50m12aa01 is a 5500 watts or 5 5 kilowatts water tank.
120 volt elements consume 1125 watts while residential 240 volt heaters use 4 500 watts.
Multiply the current rating of the water heater with 125.
Now in order to choose an electric breaker multiply the current draw of the water heater with 125 per cent in order to determine the size of the breaker you will need.
The amperage of a water heater is governed by the wattage of the heating elements and the voltage that is applied to them.
A 200 amp service allows operation of multiple appliances at once while a 60 amp service won t provide enough power to run an electric hot water heater air conditioner and hair dryer simultaneously.