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A 15-amp circuit at 120 volts supplies up to 1,800 watts, but the safe continuous limit is 1,440 watts — here is what that means for the everyday household outlets in most of your home.
15 Amps to Watts: The Standard Household Limit
At the standard US outlet voltage of 120 V, a 15-amp circuit can carry 15 × 120 = 1,800 watts at its absolute maximum. In practice, the National Electrical Code limits continuous loads (anything running three hours or more) to 80% of the breaker rating. That drops the safe, sustainable ceiling to 1,440 watts (15 × 120 × 0.8).
This is the default for general-purpose household outlets — the receptacles feeding bedrooms, living rooms, and hallways. Such circuits are typically wired with 14 AWG (American Wire Gauge) Romex cable, which is rated for exactly 15 amps and no more.
For the general formula behind any current and voltage, see our Amps to Watts calculator.
What Can You Run on a 15-Amp Circuit?
Because everyday electronics draw relatively little power, a single 15-amp circuit comfortably handles many of them at once:
- Televisions, streaming boxes, and sound bars (roughly 50–200 W each)
- Lamps and LED lighting (10–100 W)
- Laptops, desktop computers, and monitors (30–350 W)
- Phone and tablet chargers, routers, and modems (5–30 W)
- Ceiling fans and small kitchen gadgets such as a blender used briefly
A word of warning: a single high-draw appliance can swallow the whole circuit. A 1,500-watt space heater alone uses 1,500 W — more than the 1,440 W continuous limit — so it will trip the breaker as soon as anything else on the same circuit turns on. High-wattage heaters, hair dryers, and portable AC units should always run on a circuit of their own.
15-Amp Conversion Chart
Because watts depend on voltage, the same 15 amps delivers very different power at each common voltage:
| Voltage | Watts |
|---|---|
| 12 V | 180 W |
| 120 V | 1,800 W |
| 240 V | 3,600 W |
Frequently Asked Questions
What is Ohm's Law? +
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, expressed as V = I × R (Voltage = Current × Resistance). It's the foundation for calculating power, where Watts = Amps × Volts.
How do I convert watts to kilowatts? +
Divide the number of watts by 1,000. For example, 2,500 watts equals 2.5 kilowatts. Kilowatts are typically used to describe larger loads and to measure energy consumption on your utility bill.
How is my electricity bill calculated? +
Utilities charge per kilowatt-hour (kWh). Multiply an appliance's power in kilowatts by the hours it runs to get kWh consumed, then multiply by your electricity rate. The Energy Cost tab above does this automatically for daily, monthly, and yearly estimates.
What is a kilowatt-hour (kWh)? +
A kilowatt-hour is a unit of energy equal to running a 1,000-watt appliance for one hour. It is the standard unit used by energy providers to measure and bill electricity usage.