Adding 3-phase service: often more involved than expected.
Converting from single-phase to 3-phase service is a substantial project — PG&E transformer change, new service entrance, new panel, and complete rewiring of any equipment requiring 3-phase. Here's the scope.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Adding 3-phase service to a building currently on single-phase service involves: PG&E transformer change (PG&E scope, 4-8 weeks coordination), new service entrance from transformer to meter (PG&E scope), new meter base (PG&E and us), new main service panel (our scope), and any equipment changes to take advantage of 3-phase. Total project: 8-14 weeks, $25,000-$70,000 typical Marin small commercial. Only justified if 3-phase equipment loads are substantial or planned — not for general 'upgrade' without specific equipment driver.
01When 3-phase conversion is justified.
Single-phase residential service handles most general commercial loads — office equipment, retail lighting, small kitchen equipment all run on single-phase 240V split-phase. Adding 3-phase makes sense for specific equipment drivers: large HVAC equipment requiring 3-phase (typical for commercial buildings over 10,000 sq ft), commercial kitchen equipment specified for 3-phase (large ranges, commercial dishwashers above certain sizes), motor-heavy equipment (manufacturing, large pumps, industrial mixing), elevator service for multi-story buildings.
Conversion isn't justified for general 'we should upgrade' reasoning. The cost ($25,000-$70,000 typical small commercial) is substantial; without specific equipment driver, the upgrade adds capacity without operational benefit. We sometimes redirect homeowner-style 'I want 3-phase' conversations toward identifying whether there's an actual operational need before quoting the scope. Often there isn't, and a 200A or 400A single-phase upgrade serves the actual need at lower cost.
02What the project scope actually includes.
PG&E transformer change
Existing single-phase transformer must be replaced with 3-phase unit. PG&E scope. Long lead time (4-8 weeks typical for small commercial transformer change). Requires PG&E engineering review of feeder capacity to support the change.
New service entrance
From transformer to meter, new service conductors sized for 3-phase. PG&E coordinates with us on service entrance specifications. Sometimes requires above-ground conduit or trenching if existing service path doesn't accommodate 3-phase conductor count.
New main panel
3-phase main panel replacing existing single-phase panel. 3-phase panels are physically larger (third bus bar plus space for 3-pole breakers), require more wall space and proper working clearances. Typical install includes panel replacement, new main breaker, branch circuit migration.
03Alternatives to consider before committing.
For some scenarios, alternatives to full 3-phase conversion are favorable. Phase converter: rotary or static phase converter creates 3-phase power from single-phase input, supporting limited 3-phase equipment without service conversion. $3,000-$8,000 for typical residential-style phase converter. Works for small motor loads; limitations on larger 3-phase loads. Step-up transformer: 480V supply via step-up transformer from single-phase 240V. Limited application but works for specific equipment.
Most Marin commercial buildings benefit more from single-phase service upsize (200A to 400A or 600A) than from phase conversion. Single-phase 600A provides 144 kVA capacity — sufficient for most general commercial operations without the cost and complexity of 3-phase. We push to understand the actual operational driver before quoting 3-phase conversion; sometimes the answer is upsizing single-phase instead.
Common questions.
How much does single-to-3-phase conversion cost?
Marin small commercial: $25,000-$70,000 typical, varies significantly with PG&E scope, panel size needed, distance from transformer, and existing equipment compatibility. Larger commercial buildings 2-3x this range. The PG&E scope (transformer change, service entrance) accounts for $8,000-$25,000 of total; remainder is our scope (panel, internal wiring, equipment connections).
How long does it take?
Total project 8-14 weeks from contract signing. PG&E coordination is the longest pole (4-8 weeks for transformer change and engineering). Permit and AHJ plan review run parallel (3-5 weeks). Installation 1-3 days actual work. Inspection 1 week after. We coordinate the multi-party timing throughout.
Do I really need 3-phase?
Depends on equipment requirements. If you have or are adding equipment that specifically requires 3-phase (large HVAC chillers, commercial kitchen with 3-phase equipment, manufacturing motors, elevator), then yes. If general upgrade reasoning without specific equipment driver, often the answer is single-phase upsize instead. We help differentiate during planning.
Can I use a phase converter instead?
For limited 3-phase equipment needs (small motors, limited equipment count), phase converters are a meaningful alternative. Rotary phase converters work well for single significant 3-phase load; static converters work for smaller loads. Cost $3,000-$8,000 vs full conversion at $25,000-$70,000. Works when equipment count is small; doesn't scale to multi-equipment 3-phase needs.
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.