NEC 705.11 supply-side (line-side) connection, explained

When a home's main panel busbar can't absorb another backfeed breaker, installers reach for a supply-side connection under NEC 705.11. Instead of landing the PV on the load side of the main breaker, you tap ahead of the service disconnect — on the utility side — which changes the rules that apply and often unlocks a system that otherwise wouldn't fit.

Load-side vs supply-side, in one picture

Why installers choose it

The most common driver is the 120% busbar rule. On a 200 A panel with a 200 A main, load-side math caps the backfeed breaker (often at 40 A), and a larger PV system simply won't fit. Because a supply-side connection lands before the service disconnect, it is not a busbar backfeed at all — 705.12 does not govern it, so a bigger system becomes possible without a panel upgrade or a main-breaker derate.

What 705.11 requires

A supply-side connection is not a free pass; it carries its own requirements:

• Connection point: on the supply (line) side of the service disconnecting means, made with listed connectors or a tap that the utility permits.
• Overcurrent protection: the PV output conductors need overcurrent protection sized to the inverter output current — typically a fused AC disconnect.
• Disconnecting means: a readily accessible disconnect for the PV, frequently the same fused disconnect, so the system can be isolated.
• Conductor rating: the tap conductors must be rated for the PV output and protected; they are not unlimited-length taps.

A subtle point: a supply-side connection sits ahead of the service overcurrent device, so the PV system's own OCPD is what protects those tap conductors. That makes correct fuse sizing and a properly rated disconnect enclosure especially important — there is no upstream main breaker backing them up. The connection is also limited to the number of service disconnects the Code allows, so it does not become a way to add a seventh service disconnect.

Sizing the fused disconnect

The fuse and conductors follow the inverter continuous output current times 125%, the same continuous-load basis used elsewhere for PV output circuits. Size the conductor ampacity to that value, then pick a standard fuse from 240.6 and verify the conductor against the 310.16 ampacity tables. The disconnect enclosure and fuse rating must match the AC voltage of the service.

Utility and AHJ coordination

A supply-side tap touches the utility's service conductors, so it almost always needs utility approval and sometimes a specific tap method or lug the utility specifies. Meter-main combos and certain service configurations may not allow a supply-side connection at all. Confirm both the enforced NEC edition and the utility's interconnection rules before committing to this approach — our permit guides by jurisdiction track which utilities favor line-side connections.

For the load-side alternative and how the busbar math constrains it, compare with our note on why permits get rejected, where over-fused busbars are a recurring theme.

OneLine Studio is a design aid, not a permitting authority. Verify the enforced code and local amendments with your AHJ and utility, and have a licensed electrician or PE review, sign and stamp the interconnection before you file or energize.

Educational reference, reviewed 2026-07. A design aid, not a substitute for a licensed electrician or PE. Confirm the enforced NEC edition and local amendments with your AHJ.