How Many Amps Does an Engine Block Heater Use?
Engine Block Heater draws about 6.7 amps at 120 volts (800 watts running). At 6.7 A, an engine block heater fits comfortably on a standard 15 A or 20 A household circuit.
Amps = watts ÷ volts. Enter the wattage from your appliance's nameplate or label for an exact figure.
Current draw — an engine block heater
6.7 A
- At 120 V
- 800 W
- Typical breaker
- 15 A
Breaker figure is guidance for a simple resistive load, sized at 125% for continuous running — confirm against the nameplate and a licensed electrician.
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.
| Draw | Watts | Amps at 120 V | Amps at 240 V |
|---|---|---|---|
| Running | 800 W | 6.7 A | 3.3 A |
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.
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