400-amp service: for full electrification.
400-amp service handles fully-electrified large homes (heat pump + EV + induction range + electric water heater + future expansion) and small commercial. Significant upgrade from typical 200A residential.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
400A service install scope: PG&E service request and coordination, 400A meter base or two-meter configuration, 400A main switchgear, riser conduit and conductors, MDP feeding 200A distribution panels (typically split into 2x 200A sub-panels). Marin install $18,000-$45,000 typical depending on existing infrastructure and complexity. Timeline 8-16 weeks including PG&E. Common for larger Marin homes adding EV charging, heat pump HVAC, or planning future electrification.
01When 400A is the right size.
Standard residential service in Marin is 200A; that capacity handles typical homes including modern HVAC and basic electrification. 400A service becomes necessary when total simultaneous load exceeds 200A capacity: large homes (5,000+ sq ft) with multiple HVAC zones, fully-electrified homes (heat pump + induction range + electric water heater + EV charging), homes with multiple EV chargers at high amperage (two Level 2 chargers at 60A each), commercial uses in residential structures (in-law units with kitchens, home offices with equipment loads).
Load calculation determines whether 400A is needed. NEC Article 220 prescribes the calculation method: dwelling unit load calc includes lighting/receptacles, appliances, HVAC, plus heaviest of EV/electric water heater/other major loads. If calculated load exceeds 200A (typically 48,000W for 240V single-phase service), 400A upgrade is warranted. We perform load calc during quote phase using actual or planned equipment specifications.
02Configuration options.
Single 400A main with split sub-panels
One 400A meter and main breaker, distributing to two 200A sub-panels (typically one indoor for general loads, one for EV/heavy loads). Most common Marin residential configuration. Cleaner panel directory and load management.
200A/200A meter configuration
Sometimes called a 'mobile home main' or 'gang meter' configuration — two 200A meter sockets fed from common service. Each 200A meter has its own main breaker. Used for dwelling unit + ADU configurations or to separate EV/heat pump loads from general loads.
Service equipment selection
Square D QO, Eaton CH, Siemens or comparable commercial-grade for 400A service. Indoor vs outdoor location, NEMA rating per environment. Modern 400A panels often include built-in surge protection (Type 2 SPD).
03Marin install considerations.
PG&E coordination is more involved for 400A than 200A. Typical 400A install requires transformer evaluation (PG&E may need to upgrade transformer for new service load), service entrance routing (sometimes underground conversion required), and longer PG&E timeline (6-12 weeks vs 3-6 for 200A). Site survey and PG&E preliminary review establish actual timeline for your specific property.
Cost variables: distance from utility transformer (longer service entrance = more expensive), overhead vs underground service (underground costs more if existing service is overhead), existing infrastructure (mast in good condition vs needing replacement), interior service location (existing service location vs relocating panel). We provide detailed quote after site survey and PG&E preliminary review.
Common questions.
Do I really need 400A or is 200A sufficient?
Most Marin homes don't need 400A — standard 200A handles typical loads including modern appliances and even moderate EV charging. 400A becomes necessary for larger homes with multiple major electric loads. Honest answer: oversizing service is wasteful (higher install cost, sometimes higher PG&E monthly demand charges for commercial). We perform actual load calc and recommend service size based on calculated need, not maximum-possible specification.
What's the timeline for 400A install?
8-16 weeks typical from contract to operational. Breakdown: 1-2 weeks contracting and planning, 2-4 weeks PG&E preliminary review, 6-12 weeks PG&E equipment and scheduling, 1-3 days install work, 1-2 weeks AHJ inspection. Some steps overlap (PG&E timeline accommodates our install work). Faster timelines possible occasionally; slower timelines if PG&E requires transformer upgrade.
Can I phase the upgrade to 400A?
Possible but unusual. Some homeowners install 400A service entrance and main panel but only build out one side immediately, leaving capacity for future expansion. Adds modest cost upfront vs deferred upgrade cost. Most homeowners doing 400A upgrade are responding to specific load needs that justify full scope immediately.
How does this affect my PG&E bill?
Service capacity (200A vs 400A) doesn't directly affect residential PG&E billing — billing is based on actual kWh consumption, not service capacity. Larger service capacity enables more potential consumption, but only what you actually use is billed. Residential customers don't have demand charges; commercial customers sometimes do, in which case service sizing has subtle billing implications worth discussing during planning.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
Talk to a licensed electrician in Marin.
Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.