Solar, Batteries & Backup Power
Electrical Requirements for Home Solar
The roof gets the attention, but the electrical panel decides how a solar system connects — and sometimes whether a panel upgrade is part of the project.
Updated 2026-10-15
The 120% rule
For load-side connections, NEC 705.12 limits the sum of 125% of the inverter output current plus the main breaker rating to 120% of the busbar rating. On a 200A bus with a 200A main, that allows about 40A of breaker, or roughly a 32A inverter output. Larger systems need another approach.
Ways around a small busbar
Electricians commonly use:
- Main-breaker derate (e.g., 200A main to 175A) if the load calculation allows
- Supply-side (line-side) tap ahead of the main breaker
- Panel replacement with a higher-rated busbar
- Center-fed panels or solar-ready panels with dedicated provisions
Rapid shutdown, disconnects, and labeling
NEC 690.12 requires rapid shutdown for rooftop arrays so firefighters can de-energize conductors on the roof. Utilities often require a visible, lockable AC disconnect near the meter, and the code requires specific warning labels at the panel and service. These are inspection items, so ask your installer how they'll be handled.
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Frequently asked questions
Do I need a licensed electrician for solar?
The electrical portion of a solar install must be done under a license that covers it — an electrical contractor or a solar specialty license, depending on your state.
Will solar keep my power on during an outage?
Grid-tied solar without a battery shuts off during outages for line-worker safety. You need a battery or a specific backup-capable inverter for outage power.
Can I add more panels later?
Often, but busbar limits and inverter capacity may require electrical changes. Mention expansion plans at design time.
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This guide is general information, not engineering or legal advice. Electrical codes are adopted and amended locally — consult a licensed electrician and your local building department for your project.