What each panel size supports
| Panel size | What it generally supports | Typical home era |
|---|---|---|
| 60 to 100A | Lights, outlets, and a limited set of larger loads | Pre-1980 |
| 125A | The above plus one major electric system, like central AC or a heat pump | 1980s to 2000s |
| 200A | Heat pump plus an EV charger plus electric appliances | Modern standard |
| 320A (split 200/200) | Multi-EV households, fuller electrification, an ADU | Larger or newer homes |
| 400A | The above plus a workshop, pool or spa, or a large home | Premium or large homes |
For most Seattle homeowners going electric, 200A is the standard answer. For homes planning to stack several large electric loads (two EVs, an induction range, a heat pump, and a heat pump water heater) within a few years, 400A often makes more sense, because upgrading twice is more expensive than going bigger once.
How to actually size a panel
The right way is a load calculation based on your home’s actual circuits and how they are used, not a square-footage shortcut. A proper calculation accounts for the reality that not every circuit runs at the same moment. We run that calculation against your specific home, the appliances you have, and the ones you plan to add.
The general pattern: a home running mostly gas appliances has a lot of headroom on a modern panel. As you electrify, heating, an EV charger, an induction range, and an electric water heater, you use up that headroom. At some point the panel becomes the bottleneck for the next thing you want to do, and that is the moment to size up.
When 100A is still fine
Your current 100A panel may be perfectly fine if:
- You have no electric heating or cooling.
- You have a gas range and gas water heater.
- You have no EV charger.
- Your appliances and lighting are standard.
Plenty of older Seattle homes still run comfortably on 100A service for their current load. The trouble starts when you begin adding electric upgrades and the panel runs out of room.
When 200A is the right answer
200A handles most modern Seattle homes adding:
- One heat pump
- One Level 2 EV charger
- Standard appliances
- Some garage or workshop outlets
If you are adding all of that, but not a second EV and not an induction range, 200A handles it cleanly.
When to skip 200A and go straight to 400A
A few situations point to 400A:
Two or more EV chargers. A second charger can push a typical home past 200A. Going larger avoids needing a load-management device to throttle charging.
Full electrification with an induction range. A heat pump, induction range, two EV chargers, and a heat pump water heater together can exceed 200A. A larger panel handles it without throttling.
A workshop, pool, spa, or ADU. Each of these adds significant dedicated capacity. Once you are stacking large discretionary loads, a bigger panel becomes the cleaner answer.
Larger homes. More circuits, more outlets, more major appliances. Even without aggressive electrification, a large home benefits from a bigger panel.
A multi-year electrification plan. If you know a second EV charger, an induction range, or a heat pump water heater is coming within a few years, the bigger panel now is cheaper than upgrading twice. The labor and permit work do not change much between sizes; the equipment is the difference.
