Difference Between 120 Volt and 240 Volt | What Each Powers

A 240V circuit delivers about twice the wattage of a 120V circuit at the same amperage — which is why big appliances use 240V.

For the full breakdown, see our best 120 Volt Oven guide.

U.S. households run on two voltages at once, and most people only think about the difference between 120 volt and 240 volt the day a new dryer won’t start or an outlet starts buzzing. The reason one panel feeds both is split-phase service: the transformer outside supplies two 120-volt legs. Either leg to neutral reads 120V; leg to leg reads 240V. So the same breaker box can power a bedroom light and an electric range at the same time.

What The Voltage Numbers Actually Mean

120V and 240V are nominal ratings, not exact meter readings; household voltage drifts a few volts around those targets. Officially, residential service in the U.S. is described as 120 volts and 240 volts. The “220V” you still hear in conversation is older informal wording for the same supply, and today’s equipment is rated for the modern 240V standard.

Wiring explains the practical difference. A 120V circuit uses one hot conductor and a neutral conductor. A 240V circuit uses two hot conductors — the two legs of the split-phase supply — which is why it needs a double-pole breaker at the panel. When a label says “120V only,” the device stays on the single-leg circuit. When it says “240V,” it expects both legs.

Why 240V Delivers Roughly Twice The Power

The difference that matters most is wattage. Power equals voltage times amperage, so at the same current a 240V circuit moves about twice the watts of a 120V one. On a 15-amp circuit — a common household size — 120V delivers 1,800 watts and 240V delivers 3,600 watts. High-demand appliances simply need that extra headroom.