How Many Amps Does an Electric Water Heater Use?

An electric water heater uses about 18.8 running amps at 240 volts (roughly 4,500 watts). To get your unit's exact draw, divide the nameplate watts by 240: amps = watts / volts. A standard 4,500 W / 240 V electric water heater draws 4,500 / 240 = 18.75 A (about 18.8 A) from its heating element. NEC 422.13 treats a fixed storage water heater as a continuous load, so the circuit is sized at 125% (23.4 A) onto a 30A / 240V circuit with 10 AWG copper. A heat pump (hybrid) water heater has the same 4,500 W backup element and wires the same way, but in heat-pump mode it draws only a few amps, and the newer 120V plug-in hybrids draw far less and can sometimes share a circuit. The nameplate always governs.

An electric water heater belongs on a dedicated 30A / 240V circuit (NEC 422.13, 422.11(E)). At 18.8 running amps it stays within the 80% continuous limit of that breaker. Do not put it on a shared circuit with other large loads.

Divide the wattage on the nameplate by the voltage: amps = watts / volts. An electric water heater at about 4,500 watts on 240V works out to 4,500 / 240 = 18.8 amps. The nameplate always governs over a typical value.

Same answer: water heater is another name for an electric water heater. It draws about 18.8 amps at 240V on a dedicated 30A circuit. A standard 4,500 W / 240 V electric water heater draws 4,500 / 240 = 18.75 A (about 18.8 A) from its heating element. NEC 422.13 treats a fixed storage water heater as a continuous load, so the circuit is sized at 125% (23.4 A) onto a 30A / 240V circuit with 10 AWG copper. A heat pump (hybrid) water heater has the same 4,500 W backup element and wires the same way, but in heat-pump mode it draws only a few amps, and the newer 120V plug-in hybrids draw far less and can sometimes share a circuit. The nameplate always governs.