Wiring Basics
Plain-English home wiring basics: matching wire size to breaker size, 120-volt vs 240-volt circuits, and what grounding and bonding do.
A little background goes a long way when you're planning a project or talking with an electrician. These guides cover wire and breaker sizes, 120 vs 240 volts, and what grounding and bonding actually do, in plain English.
Guides in this section 3
Wire size and breaker size: how they go together
Why wire gauge has to match breaker size, common copper sizes for 15 to 60 amps, aluminum, temperature ratings and voltage drop on long runs.
Read guide Wiring Basics120 volts vs 240 volts in your home
How a home gets both 120 and 240 volts, which appliances need 240V, double-pole breakers, outlet shapes and what that means for EV chargers.
Read guide Wiring BasicsGrounding and bonding basics for homeowners
What grounding and bonding do, ground rods and Ufer grounds, why neutral and ground separate in subpanels, and bonding gas and water piping.
Read guideHelpful tools
Wire size calculator
Free wire size calculator: enter amps, copper or aluminum, and distance to see the minimum AWG by NEC 310.16 ampacity and for 3% voltage drop. Rough guide.
Open tool ToolVoltage drop calculator
Free voltage drop calculator: enter wire size, copper or aluminum, amps and one-way distance to see volts lost and percent drop. NEC Chapter 9 Table 8 values.
Open toolMore sections
- Panels & Service Upgrades
- EV Chargers
- Generators & Battery Backup
- Solar
- Safety & Hazards
- Older Homes & Old Wiring
- Troubleshooting
- Permits & Inspections
- Lighting & Outlets
- Calculators & Tools
General information for California homes. Local rules and inspectors can vary. Not a substitute for an on-site inspection.