Electrical current — measured in amperes — determines wire size, breaker ratings, and safety in your home. Too much current through too-small a wire creates heat, which causes fires. Understanding current ratings is essential for electrical safety.
Wire Gauge and Current Capacity
Wire gauge (AWG in the US) determines how much current a wire can safely carry. This is called "ampacity."
- 14 AWG: 15 amps — standard lighting circuits
- 12 AWG: 20 amps — standard outlet circuits
- 10 AWG: 30 amps — dryers, water heaters
- 8 AWG: 40 amps — ranges, large heaters
- 6 AWG: 55 amps — sub-panels, EV chargers
- 4 AWG: 70 amps — main panels in small homes
Using wire that's too thin for the current causes overheating. The circuit breaker protects the wire, not the device.
Circuit Breaker Selection
Breakers are rated slightly below the wire's maximum ampacity. A 15A breaker on 14 AWG wire protects the wire from carrying more than 15A.
Standard residential breakers: 15A (lighting), 20A (outlets), 30A (dryers), 40A (ranges), 50A (EV chargers, workshops). The main breaker is typically 100–200A.
Never replace a breaker with a larger one without also upgrading the wire. This is a common cause of electrical fires.
Typical Household Current Draw
- LED light: 0.05–0.1 A
- Phone charger: 1–2 A
- Microwave: 10–12 A
- Hair dryer: 12–15 A
- Space heater: 12–15 A
- Central AC: 15–30 A
- EV charger: 32–48 A (continuous)
Two high-draw devices on the same 15A circuit will trip the breaker. This is why kitchens and laundry rooms have multiple dedicated circuits.
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