How Many Amps Does a Space Heater Use?

Space Heater amperage at 120 V and 240 V

Same 1,500 W load: the current halves when the voltage doubles. Space Heater is typically a 120 V appliance in US homes.

Breaker and circuit for a space heater

At 13 A, a space heater is too much for a shared 15 A circuit under the 80% rule; it belongs on a 20 A circuit, ideally with little else running on it. For a dedicated circuit, guidance is a 20 A breaker with 12 AWG copper (75°C terminations), sized at 125% of the running current because it runs 3+ hours at a time (NEC 210.20).

Guidance only: actual circuit sizing depends on your unit's nameplate, wire run length, and local code. Confirm with a licensed electrician. See the wire & breaker size chart for the full NEC ampacity table.

Measure what a space heater actually draws

The figures above are typical ratings. A plug-in power meter between the outlet and the cord shows the real amps and watts with nothing opened up. A clamp meter reads one conductor at a time, so it is the tool for hardwired and 240 V circuits; clamped around a whole cord it reads close to zero.

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Plug-in power meter

P3 International Kill A Watt P4400

Best for: Measuring what one plug-in appliance really uses

Check price on Amazon: P3 International Kill A Watt P4400 (opens in a new tab)(paid link)

Clamp meter

Fluke 323

Best for: Measuring what a hardwired circuit actually draws, even in a crowded panel

Check price on Amazon: Fluke 323 (opens in a new tab)(paid link)

Frequently asked questions

Amp draw of other appliances

• Window Air Conditioner10 A
• Central Air Conditioner15 A
• Heat Pump13 A
• Ceiling Fan0.5 A