200A Service Upgrade: Complete Wiring Guide
Bill of materials
A 200A service upgrade is the most significant residential electrical project. It involves replacing the meter base, service entrance cable, main panel, and grounding system. Always requires a licensed electrician.
A 200A dwelling service uses 2/0 AWG copper or 4/0 AWG aluminum per NEC Table 310.15(B)(7), which permits smaller conductors than Table 310.16 for 120/240V single-phase dwelling services. Requires a 200A main breaker panel, meter base, and proper grounding per NEC 250.52 (two ground rods minimum 6 feet apart, or one rod with supplemental electrode).
200A dwelling service
| Component | Specification | NEC basis |
|---|---|---|
| Wire (copper) | 2/0 AWG THHN | Table 310.16, 110.14(C) |
| Wire (aluminum alt.) | 4/0 AWG THHN | Table 310.16, 110.14(C) |
| Breaker | 200A double-pole | 240.4 |
| Voltage | 240V single-phase | |
| Conduit (EMT) | 2" EMT | Chapter 9 Table 4 |
| Max distance (3% VD) | 232 ft at 240V copper | 210.19(A) Note 4 |
Installation notes
GFCI is not specifically required for this application by NEC, though local amendments may differ. Check with your local building department before starting work.
For the wire run, you have two options: NM-B cable (Romex) for interior runs through framing, or individual THHN conductors in conduit for exposed runs, outdoor installations, or runs through unfinished spaces. NM-B is faster to install but cannot be used outdoors or in conduit. For conduit, use EMT (metallic) or PVC Schedule 40.
Run length matters: every foot of wire adds voltage drop, reducing power to your equipment. The table below shows the exact voltage drop at common distances. If your run exceeds the 3% threshold, upsize one gauge.
Voltage drop by distance
Percentage voltage drop at common run lengths. NEC recommends 3% maximum for branch circuits and 5% for combined feeder plus branch.
| Distance | 2/0 AWG Co | 4/0 AWG Al | 3/0 AWG Co |
|---|---|---|---|
| 25 ft | 0.3% | 0.3% | 0.3% |
| 50 ft | 0.6% | 0.7% | 0.5% |
| 75 ft | 1.0% | 1.0% | 0.8% |
| 100 ft | 1.3% | 1.3% | 1.0% |
| 150 ft | 1.9% | 2.0% | 1.5% |
| 200 ft | 2.6% | 2.7% | 2.0% |
Common products for 2/0 AWG Copper circuits
As an Amazon Associate we earn from qualifying purchases.
Related wire data
Detailed ampacity: 2/0 AWG copper, 4/0 AWG aluminum. Wire size lookup: 200A circuit. Calculators: voltage drop · panel load calculator.
How NEC edition affects this project
Not every state uses the same NEC edition. The table below shows how requirements for this project differ depending on which edition your state has adopted. Find your state's edition here.
| Requirement | NEC 2023 | Earlier editions |
|---|---|---|
| Surge protection | Surge protective device (SPD) required per 230.67 | SPD not required by NEC (may be required by local amendment) |
| Load calculation | Use new Article 220 Part III simplified method | Use traditional Article 220 standard method |
| EV readiness | Consider adding EV-ready circuit per 625.40 if attached garage | No EV readiness requirement |
Currently, 17 states enforce NEC 2023, 21 use NEC 2020, 7 use NEC 2017, and 2 are still on NEC 2008. Three states (Arizona, Mississippi, Missouri) defer to local jurisdictions. Find your state to see which specific rules apply to your location.
Inspection preparation
Before your service upgrade inspection, verify these frequently-checked items:
| Check | NEC Ref | Common Fail |
|---|---|---|
| Service entrance conductors properly sized | NEC 230.42 | Undersized SE conductors for panel rating |
| Main breaker matches panel rating | NEC 230.90 | Main breaker exceeds panel bus bar rating |
| Grounding electrode conductor properly sized | NEC 250.66 | GEC too small for service size |
| Grounding electrode system complete | NEC 250.50 | Missing required electrodes (water pipe, ground rods, Ufer) |
| Two ground rods (if no Ufer/water pipe) | NEC 250.53(A)(2) | Single ground rod without resistance test or supplemental electrode |
See the full inspection checklist tool for all 13 items with progress tracking.
Frequently asked questions
What wire size do I need for 200a service upgrade?
Use 2/0 AWG copper or 4/0 AWG aluminum on a 200A breaker at 240V. This is based on NEC 2023 Table 310.16 ampacity with 110.14(C) termination limits and 125% continuous load sizing per 210.19(A)(1).
Does 200a service upgrade require GFCI?
No. GFCI is not required for this application.
NEC 2023 references verified April 2026