Panel capacity — when you need an upgrade, when load management is enough.
Short answer: Your panel's main breaker rating (100A, 125A, 150A, or 200A) sets the absolute maximum your home can draw at once. Whether you have room for a 48A EV charger depends on how much of that capacity is already used by your other appliances. NEC 220 'demand load calc' provides the math. Most 200A panels have plenty of room. Most 100A panels don't — but load management often solves it for less than a panel upgrade.
What your main breaker tells you
Look at the top of your electrical panel. The biggest breaker — usually labeled "MAIN" — has a number on it. Common ratings:
- 100A — typical for homes built 1950–1980
- 125A — transitional homes, 1970s–1980s
- 150A — some 1980s homes; rare today
- 200A — standard since 1985+; almost universal in newer construction
- 400A — premium homes and homes with multiple ADUs
The NEC 220 demand load calculation
National Electrical Code section 220 gives an actual formula for how much capacity your panel currently uses. It's not "sum of all breakers" (that would over-count — appliances rarely run simultaneously at max). It applies "demand factors" — discount factors for loads that don't typically all peak at once.
Simplified version (rough estimate)
Baseline 30A always (general lighting, outlets). Plus:
- Central A/C: +50A
- Electric dryer: +30A
- Electric range: +40A
- Electric water heater: +30A
- Pool / spa pump: +30A
- EV charger at 48A continuous: +60A (per 125% continuous-load rule)
Add them up. That's your demand load. Compare to your main breaker rating.
Worked examples
Example 1: 200A panel, gas appliances, no pool
30 baseline + 50 A/C = 80A used. 200A panel - 80A used = 120A free. EV at 60A fits easily.
Example 2: 100A panel, gas appliances, no pool
30 + 50 A/C = 80A used. 100A panel - 80A used = 20A free. EV at 60A doesn't fit. Options: load management ($1,420) or panel upgrade ($3,800+).
Example 3: 125A panel, electric appliances, no pool
30 + 50 + 30 dryer + 40 range + 30 water heater = 180A demand. 125A panel = NEGATIVE 55A. Panel is technically already over-capacity (homes "get away with it" because not everything runs simultaneously). EV install is out of the question without panel upgrade.
Load management vs panel upgrade
If your panel is 10–20A short of accommodating the EV, load management ($1,420) is the cleaner answer. The device pauses one big appliance while another runs.
If your panel is 30+ amps short, or if you're planning multiple electrification upgrades (heat pump, induction range, electric water heater, etc.), panel upgrade is the right path.
What the network installer determines at the panel check
- Actual demand load using NEC 220 math (not the simplified version above)
- Breaker space availability (separate question from capacity — sometimes panels are full of small breakers)
- Service-entrance conductor sizing (sometimes the panel is 200A but the wires from the utility are smaller — limits the upgrade path)
- Utility coordination requirements (SMUD, PG&E, Roseville Electric all have different processes for upgrades)
Don't trust your own demand load math. The simplified version above is for ballpark; NEC 220 has more nuance (HVAC vs heat pump factors, dwelling-unit load tables, etc.). Network installers do the real calc at the panel check, and it's free. The right answer might surprise you in either direction.