How Many Amps Does an Engine Block Heater Use?

Engine Block Heater amperage at 120 V and 240 V

Same 800 W load: the current halves when the voltage doubles. Engine Block Heater is typically a 120 V appliance in US homes.

Breaker and circuit for an engine block heater

At 6.7 A, an engine block heater fits comfortably on a standard 15 A or 20 A household circuit. For a dedicated circuit, guidance is a 15 A breaker with 14 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 an engine block 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

• Pool Pump4.6 A
• Hot Tub17 A
• Level 2 EV Charger40 A
• Garage Door Opener4.6 A