What Size Wire for an Electric Water Heater?
Wire and breaker sizing for an Electric Water Heater — the typical 240V circuit, plus the code details (NEC 310.16) that change the answer.
Calculations are built on the 2023 National Electrical Code (NEC) and cross-checked against the published code tables. How we verify. Last reviewed June 2026.
Copper
10 AWG
On a 30A 240V circuit at 75°C terminations.
Aluminum
8
Protected by a 30A breaker (NEC 240.6).
Voltage
240V
Breaker
30A
Connection
Hardwired
GFCI
Not required
Electric Water Heater Circuit Details
- A standard 4,500W tank water heater draws 18.75A and uses a 30A 240V circuit — 10 AWG copper.
- Water heaters are treated as continuous loads (NEC 422.13), but a 30A breaker with 10 AWG already covers the 125%.
- Confirm the element wattage on the data plate.
Long run to your electric water heater?
Over distance, voltage drop can require a larger wire than the table above. See the 30A wire size by distance:
Size it for your exact install
Open the calculator pre-filled with 30A at 240V to add distance, material and temperature.