100A vs 200A vs 400A Electrical Panels.

TL;DR. 200A is the right answer for most Seattle homes electrifying in 2026 (heat pump + one EV + standard appliances). Skip to 400A if you have 2+ EVs, planned induction range, or a 5-year full-electrification plan, because upgrading twice is more expensive. 100A is still viable if you have no electric heat, no AC, no EV, and no induction.

Direct answer, what each panel size supports

For most Seattle homeowners electrifying in 2026, 200A is the standard answer. For homes adding 2+ EVs, induction range, heat pump, and a heat pump water heater within a 5-year window, 400A makes the math better because upgrading twice is expensive.

How to actually size the panel

Real load calculation, not square footage rules. Two methods:

For a typical Seattle home considering electrification:

Total demand load: 47,290 W = roughly 197A at 240V

This is right at the edge of a 200A panel. Add a second EV charger or a hot tub and you’re over capacity, which means 200A is workable but tight, and 320A or 400A would give breathing room.

When 100A is still fine

Your current 100A panel is probably fine if:

• No electric heating or cooling (gas furnace, no AC)
• Gas range and gas water heater
• No EV charger
• Standard appliances (dryer, dishwasher, washer)
• Standard lighting

Roughly 25 to 30 percent of pre-1985 Seattle homes still have viable 100A service for their current load. The problem comes when you start adding electrification, and the panel becomes the bottleneck for everything you want to do next.

When 200A is the right answer

200A works for most modern Seattle homes adding:

• One heat pump (4-ton or smaller)
• One Level 2 EV charger
• Standard appliances
• Some workshop or garage outlets

If you’re adding all of the above but no second EV and no induction range, 200A handles it cleanly.

When to skip 200A and go straight to 400A

Several scenarios where 400A is the right answer:

Multi-EV households (2+ Level 2 chargers). A second Level 2 charger pushes load past 200A capacity in most homes. Without 400A, you need a load-management device that throttles charging when other appliances run. Load management works but adds complexity.

Full electrification with induction. Heat pump + induction range + 2 EV chargers + HPWH brings total demand load over 200A even with diversification. 320A or 400A handles it without throttling.

Workshop, pool, spa, or ADU. Any of these adds 30 to 100 amps of dedicated capacity. Once you’re stacking large discretionary loads, 400A becomes the cheaper answer.

Larger homes (3,500+ sq ft). More lighting circuits, more outlets, more major appliances. Even without aggressive electrification, larger homes benefit from 320A or 400A service.

5-year electrification plan. If you know you’ll add a second EV charger, induction range, or HPWH within 5 years, doing the bigger panel now is cheaper than upgrading twice. The labor and permit costs don’t change much between 200A and 400A; the equipment cost adds $2,500 to $4,500.

The cost difference, real Seattle numbers

Federal 25C tax credit covers up to $2,000 of the panel upgrade when it’s required to enable a heat pump install.