What Size Breaker for Electric Water Heater?
A electric water heater requires a 30A breaker with 10 AWG wire on a 240V dedicated circuit. This is a continuous load — breaker rated at 125% of actual draw.
🔌 Wire Length & Voltage Drop Check
Electric Water Heater Wiring Guide — NEC Requirements
Electric water heaters are considered a continuous load per NEC 422.13. A 4500W heater draws 18.75A at 240V, requiring a 30A breaker (18.75A × 125% = 23.4A → 30A).
Pro Tip
💡 Water heaters must be on a dedicated circuit. The disconnect must be within sight of the unit or lockable per NEC 422.31.
Why a 30A Breaker?
The electric water heater draws approximately 18.75A at 240V (4500W). As a continuous load (3+ hours), NEC 210.20 requires the breaker at 125%: 18.75A × 1.25 = 23.4A → 30A breaker.
Wire Sizing per NEC 310.16
For a 30A/240V circuit, 10 AWG copper is required per NEC Table 310.16 at 75°C. For runs over 75 feet, upsize to 8 AWG (long runs). Use our Wire Size Calculator and Voltage Drop Calculator.
Complete Parts List
To wire a electric water heater circuit: a 30A double-pole breaker, 10 AWG NM-B cable (Romex) for interior runs or THHN/THWN-2 in conduit for exposed runs, a NEMA 14-30 receptacle (or hardwired), cable clamps, and appropriate junction boxes.
Disclaimer: This guide is for reference only. All electrical work must be performed by or verified by a licensed electrician. Local codes may differ from NEC.