Most Bay Area homes built before 1990 were wired for a very different household: gas heat, gas cooking, and one car in the driveway. Electrification changes that math quickly.
A load calculation is the honest answer. It adds your existing demand to planned additions — EV charging, heat pump, induction range — and compares the total to your service rating. Plenty of 100A services still have room, especially with load-management devices that pause charging when the dryer runs.
Where an upgrade makes sense is when you plan two or more major electrification projects, when your panel is a recalled brand, or when there is simply no space for new breakers. In those cases the upgrade pays for itself by eliminating repeat trips and permitting.
If you're unsure, a diagnostic visit with a written load study costs far less than guessing wrong in either direction.
Questions about your own home? Request a visit or call (415) 555-0142.