Electrical Service Upgrades: Panels, Load Calcs, and EV Readiness
When 200 amps isn't enough and how to plan for full electrification.
Heat pumps, induction ranges, heat-pump water heaters, EV chargers, and rooftop solar with battery storage have made the 100-amp panel obsolete and stretched 200-amp panels on whole-home electrification projects. This article covers when to upgrade, how to calculate it correctly, and what the utility will and won't approve.
NEC load calculation basics
NEC Article 220 governs residential load calcs. Standard method: 3 VA/sf general lighting + small appliance circuits + largest motor + nameplate of fixed equipment. Optional method (220.82): often allows smaller service for typical houses. A licensed electrician must perform the calc; plan-check will reject hand-waved upgrades.
When to upgrade from 100A to 200A
EV charger (40A circuit, 32A continuous), heat-pump HVAC (typically 30–60A), heat-pump water heater (30A), induction range (50A), and a panel that can hold the new breakers. Most pre-1980 houses are 100A; whole-home electrification typically requires 200A minimum.
Going beyond 200A
400A residential is common in 4,000+ sf homes or homes with multiple ADUs. Requires a meter-main combo, often with two separate sub-panels. Utility service drop may need upgrading (transformer-side work). LADWP and PG&E both publish service requirement guides; budget 6–16 weeks for utility coordination.
Load management as an alternative
Pacific Energy, Span, Schneider Square D Energy Center, and Lumin offer smart panels and circuit-level load management. These allow 200A service to support an EV charger + heat pump + range that would exceed the legacy calc — they shed loads dynamically. Title 24 and NEC 750 recognize these in load calculations.
Solar and battery interconnection
California's NEM 3.0 (now Net Billing Tariff) drastically changed solar economics. Battery storage paired with solar restores value. Interconnection requires utility approval; supply-side taps and main panel upgrades are common adjacent scopes. Coordinate with the electrician and solar installer at design development.
Authoritative sources
- 2023 National Electrical Code (NFPA 70) — National Fire Protection Association
- LADWP electrical service requirements — Los Angeles Department of Water and Power
- PG&E electric service requirements (Greenbook) — Pacific Gas and Electric
- California Net Billing Tariff (NEM 3.0) — California Public Utilities Commission
More from the library
- Residential Structural Engineering 101 for California Owners — Load paths, shear walls, and why your remodel needs an engineer's stamp.
- California Title 24 Energy Compliance: A Plain-English Guide — Why your remodel needs a HERS rater and what the energy compliance form really says.
- Seismic Retrofit Basics for California Single-Family Homes — Cripple walls, sill bolting, and the Earthquake Brace + Bolt grant program.