Choosing the right panel size is the most important decision in a main service panel upgrade. Too small, and you’ll trip breakers and limit your home’s capabilities. Too large, and you’ll spend more than necessary. Here is how to choose between 100, 200, and 400 amps.
100‑Amp Panels: The Legacy Standard. Many homes built before the 1980s have 100‑amp service. It was adequate for a time when homes had fewer appliances, no central air, and no electronics. Today, a 100‑amp panel can support a small home with gas appliances and modest electrical needs, but it’s generally considered undersized for modern living. If you’re planning to add an EV charger or heat pump, you’ll almost certainly need more.
200‑Amp Panels: The Modern Baseline. A 200‑amp panel is now the standard for most new and upgraded American homes. It supports electric ranges, dryers, central air conditioning, multiple appliances, and one Level 2 EV charger. If you’re upgrading, 200 amps is the default choice unless you have specific high‑demand needs. For more on when 200 amps is required, see our guide on panel upgrades for EV and solar.
400‑Amp Panels: For Large Homes and Heavy Loads. Homes larger than 4,000 square feet, homes with multiple EV chargers, large solar arrays, or all‑electric systems may need 400‑amp service. This is also common in homes with detached garages, workshops, or ADUs. A 400‑amp panel is a significant investment but future‑proofs your home.
How to Determine Your Needs: A licensed electrician performs a load calculation based on square footage, major appliances, and planned additions. Don’t guess. An oversized panel is wasted money; an undersized panel is a safety risk and an expensive re‑do. For help finding the right electrician, see how to choose a licensed electrician. For cost comparisons, see panel upgrade cost in the USA. And for a broader overview, start with what is a main panel upgrade.