What does 100 amp service mean?

One hundred amp service means the electrical connection feeding your house can deliver up to 100 amps at 240 volts, roughly 24,000 watts, before the main breaker opens. The number describes the service equipment: main breaker, panel bus, meter, and service conductors, all rated together.

It was the postwar standard and still serves smaller homes with gas appliances comfortably.

You can read yours off the main breaker's handle. The panel may hold many more branch breakers than the math suggests; diversity makes that legal and normal.

The ceiling matters when electrification arrives: EV charging, heat pumps, and electric ranges are what push a 100 amp house toward an upgrade.

The 100 amp service wire calculator shows the conductors that rating actually requires.