Do I need 100-amp or 200-amp electrical service?

It depends on your total calculated load, not floor area alone. The National Electrical Code sets 100 amps as the minimum service for a home, and newer homes commonly have 150- or 200-amp panels, according to a U.S. Department of Energy guide. A Lawrence Berkeley National Laboratory study found 100-amp and 200-amp panels are the most common sizes nationwide, at about 55% and 29% of single-family homes. A small, efficient home may fit on 100 amps, but adding an EV charger, electric heat pump, or a second building pushes demand up. Have an electrician run a load calculation, and leave room for future additions.

Check your local rule. This varies by state, county or city. Your permitting office has the final word; the official lookup pages below show you who that is.

Sources

• Home Electrification and Electric Panel UpgradesU.S. Department of Energy, Building Science Education Solution Center
• Characterizing Electrical Panel Capacity, Breaker Space, and Loads in U.S. Single-Family HomesLawrence Berkeley National Laboratory