How Many Amps Does a Space Heater Use?

A space heater uses about 12.5 running amps at 120 volts (roughly 1,500 watts). To get your unit's exact draw, divide the nameplate watts by 120: amps = watts / volts. A 1,500 watt space heater draws exactly 12.5 amps. A portable (plug-in) heater is not Article 424 equipment, which covers fixed heaters: on a circuit with more than one outlet, NEC 210.23(B)(1) limits one cord-and-plug item that is not fastened in place to 80 percent of the circuit, 12 amps on 15A and 16 amps on 20A, and Table 210.21(B)(2) holds a 15A receptacle on such a circuit to 12 amps, so a 1,500 W heater is within both only from a 20A receptacle on a 20A circuit. Keep it the only significant load and never on an extension cord. A heater left running for 3 hours or more is a continuous load (NEC Article 100), and NEC 422.10(A)(3) rates the circuit for an appliance that is a continuous load at 125 percent of it: 12.5 x 1.25 = 15.6A, which is why a dedicated 20A circuit is the answer here. A fixed (hardwired) heater of the same rating is Article 424: its conductors at 125% (12.5 x 1.25 = 15.6A, NEC 424.4(B)), which exceeds 15A, so it needs a 20A circuit. Two 1,500W heaters cannot share one 15A or 20A circuit.

A space heater belongs on a dedicated 20A / 120V circuit (NEC 210.22 and 422.10(A)(3) for a heater run 3 hours or more; 210.23(B)(1) and Table 210.21(B)(2) where it shares a circuit; 424.4(B) for a fixed heater). At 12.5 amps, treated as a continuous load, its circuit must be rated at least 125 percent of it (15.6A); a 20A breaker covers that. Do not put it on a shared circuit with other large loads.

Divide the wattage on the nameplate by the voltage: amps = watts / volts. A space heater at about 1,500 watts on 120V works out to 1,500 / 120 = 12.5 amps. The nameplate always governs over a typical value.

Same answer: electric space heater is another name for a space heater. It draws about 12.5 amps at 120V, on a dedicated 20A / 120V circuit. A 1,500 watt space heater draws exactly 12.5 amps. A portable (plug-in) heater is not Article 424 equipment, which covers fixed heaters: on a circuit with more than one outlet, NEC 210.23(B)(1) limits one cord-and-plug item that is not fastened in place to 80 percent of the circuit, 12 amps on 15A and 16 amps on 20A, and Table 210.21(B)(2) holds a 15A receptacle on such a circuit to 12 amps, so a 1,500 W heater is within both only from a 20A receptacle on a 20A circuit. Keep it the only significant load and never on an extension cord. A heater left running for 3 hours or more is a continuous load (NEC Article 100), and NEC 422.10(A)(3) rates the circuit for an appliance that is a continuous load at 125 percent of it: 12.5 x 1.25 = 15.6A, which is why a dedicated 20A circuit is the answer here. A fixed (hardwired) heater of the same rating is Article 424: its conductors at 125% (12.5 x 1.25 = 15.6A, NEC 424.4(B)), which exceeds 15A, so it needs a 20A circuit. Two 1,500W heaters cannot share one 15A or 20A circuit.