4,500 W water heater
Common electric tank water heater planning example.
25 APlanning breaker sizewater heater breaker size
Water Heater Breaker Size
A 4,500 watt 240 volt electric water heater is commonly planned around a 30 amp circuit, but the equipment label controls.
Inputs
Results
Immediate estimatePlanning breaker size25 A18.8 A nameplate load before adjustment
Adjusted load23.4 A
Common copper conductor10 AWG copper
Voltage240 V
Wattage4,500 W
Acknowledge the limitations before relying on this as a planning lookup.
Electrical sizing depends on the adopted NEC edition, terminal temperature ratings, insulation type, conductor material, conduit fill, derating, grounding, equipment labels, and local inspection requirements.
Diagram
Water heater circuit
Wattage and voltage are converted to load amps and a planning breaker size.
- Wattage
- Voltage
- Breaker
How this calculator works
Enter water heater wattage and voltage to estimate load amps, adjusted amps, breaker size, and common copper conductor size.
Load model
The engine divides watts by volts, optionally applies a 125 percent continuous-load adjustment, then rounds to the next standard breaker size.
Wire hint
A common copper conductor size is shown for the selected breaker rating.
Equipment caution
The nameplate, installation manual, conductor type, and adopted code must be checked before installation.
Load
watts / voltsAdjusted load
load amps x 125% when continuous load is selectedBreaker
next standard breaker sizeAssumptions
- Equipment: Resistive tank-style water heater planning estimate.
- Label controls: Use the equipment nameplate, installation instructions, and adopted code for final breaker and conductor sizing.
Worked examples
5,500 W water heater
Shows higher wattage effect.
30 APlanning breaker sizeFAQ
What breaker size for a 4,500 watt water heater?
A 30 amp circuit is a common planning answer for a 4,500 W, 240 V tank water heater.
Can a water heater use a 20 amp breaker?
Only if the wattage, voltage, conductor, and equipment instructions allow it.
Does this apply to tankless water heaters?
No. Tankless electric water heaters can require very different circuits.
Sources and review
- National Electrical Code, NFPA. Accessed 2026-07-16.
Reviewed 2026-07-20. Planning estimates only; confirm project-specific requirements.