The main breaker is the largest breaker in your electrical panel and disconnects the entire home from the utility supply. Its amperage rating — typically 100 A in older homes, 200 A in newer builds — is the total power your service can carry. Adding an EV charger or solar array means we calculate whether your existing load plus the new circuit stays under that limit. If not, options include load management (sharing capacity dynamically) or a service upgrade to a larger main.
The big breaker at the top of your panel that shuts off all power to the house. Its rating (e.g. 100A, 200A) is your service size.
