Residential EV Charger Installation: 200ft Garage Run
How proper voltage drop calculation prevented a costly callback for a Tesla Level 2 home charger installation.
Reduced voltage drop from 4.8% to 3.0%
Full 11.5kW charging power delivered
Zero callbacks or customer complaints
NEC 2023 compliant installation
Challenge
Long 200ft run from panel to detached garage requiring Level 2 EV charging at full 48A capacity
Solution
Upsized from 6 AWG to 4 AWG copper after voltage drop analysis revealed 4.8% drop
Project Overview
A homeowner in San Diego, California contacted an electrical contractor to install a Tesla Wall Connector in their detached garage. The garage, located approximately 200 feet from the main electrical panel in the house, would serve as the primary charging location for their new Tesla Model Y.
This case study demonstrates the critical importance of voltage drop calculations for long residential circuits and how proper engineering analysis prevents costly problems before they occur.
Technical Requirements
Critical Design Considerations
- • Circuit Distance: 200 feet one-way from main panel to detached garage
- • Load Current: 48A continuous charging current
- • System Voltage: 240V single-phase residential service
- • Initial Wire Selection: 6 AWG copper THWN-2
Voltage Drop Analysis
Initial 6 AWG Calculation
Vd = (2 × 48A × 200ft × 0.491) / 1000
Vd% = 3.93% - Exceeds 3% recommendation
Optimized 4 AWG Solution
Vd = (2 × 48A × 200ft × 0.308) / 1000
Vd% = 2.46% - Meets NEC recommendation
Key Takeaways
- Always calculate voltage drop for circuits over 50 feet, especially for continuous loads like EV chargers.
- EV chargers are continuous loads—size conductors at 125% of rated current per NEC 625.40.
- Material cost increases are minimal compared to callback costs and reputation damage.
Start Calculating
Ready to apply these concepts to your project? Use our professional voltage drop calculator.
Open Calculator