What Size Wire for an Electric Baseboard Heater?
Wire and breaker sizing for an Electric Baseboard 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
12 AWG
On a 20A 240V circuit at 75°C terminations.
Aluminum
10
Protected by a 20A breaker (NEC 240.6).
Voltage
240V
Breaker
20A
Connection
Hardwired
GFCI
Not required
Electric Baseboard Heater Circuit Details
- Baseboard heat is a continuous load: a 20A 240V circuit (12 AWG) safely carries about 16A / 3,840W.
- A 30A circuit (10 AWG) covers up to ~5,760W of baseboard.
- Total the connected wattage of all heaters on the circuit before sizing.
Long run to your electric baseboard heater?
Over distance, voltage drop can require a larger wire than the table above. See the 20A wire size by distance:
Size it for your exact install
Open the calculator pre-filled with 20A at 240V to add distance, material and temperature.