What subpanel means
A subpanel is a second panel fed from the main panel by a feeder, used to add circuits in a garage, addition or shop, or when the main panel is full.
Where it matters on a electrical job
In a subpanel the neutrals and grounds are kept separate, unlike the main panel. Mixing them is a common inspection failure. Price the feeder wire by length, since that is often the biggest part of the job.
What the model code says
- The code defines a feeder as the circuit conductors between the service equipment and the final branch-circuit overcurrent device. (IRC 2021, Chapter 35)
Check which code edition your building department enforces for subpanel before you quote.
What it costs
Koira's electrical panel upgrade cost guide puts a typical job at $2,150, with most between $1,300 to $3,000. The guide shows its sources and what moves the price. The voltage drop calculator prices a job line by line.
Work it out
- Free calculator: Voltage drop calculator
- Cost guide: Electrical panel upgrade cost
- Licensing: Electrical license rules by state
- Tools, templates and guides: Free electrical resources
Sources: 2021 International Residential Code, Chapter 35, Electrical Definitions (ICC). Checked October 9, 2026.