NEC 705.11(D) — When to Use a Supply-Side Tap on Solar PV Installs

The NEC 705.12 busbar rule is the bottleneck on most residential solar retrofits. It says the sum of the main breaker plus the back-fed PV breaker can't exceed 120% of the panel's busbar rating. On a 200 A panel with a 200 A main, that limits PV to 40 A back-fed (200 + 40 = 240 = 120% of 200). Bigger PV systems don't fit.

Enter NEC 705.11(D) — the supply-side connection. Instead of back-feeding a breaker on the load side of the main breaker, you tap the SERVICE-ENTRANCE conductors between the meter and the main disconnect. The PV system gets its own dedicated AC disconnect (lockable in the OPEN position, accessible to the utility) and feeds in upstream of the existing panel busbar. The 120% rule no longer applies because the busbar isn't carrying the PV current.

When to use it:

• The main breaker is already at 200 A on a 200 A panel busbar — no headroom for a back-fed breaker
• The PV system is large (typically 8 kW DC or more, depending on inverter sizing)
• The existing panel is full with no spare 2-pole space
• The main panel is a brand the AHJ doesn't want a back-fed breaker on (older Federal Pacific, Zinsco, etc. — though if it's one of those, replace it before adding PV regardless)

Required equipment for a supply-side tap:

• An AC disconnect rated for the inverter output (e.g. 60 A 2P fused for a 7.6 kW system)
• The disconnect must be lockable in the OPEN position per NEC 690.13 — meaning a standard padlock will hold it open
• Accessible to the utility — typically mounted within 10 ft of the meter, on the building exterior or in an accessible utility room
• Conductors sized for the inverter output continuous current × 125% per NEC 690.8

NJ-specific notes: PSE&G and JCPL both accept supply-side connections on residential PV. The interconnection application calls out the connection type. The AHJ typically wants the AC disconnect labeled "PV SYSTEM DISCONNECT" with a permanent label, not a sticker.

The Malfettone single-line diagram tool at /tools/single-line-diagram includes a "Solar PV with line-side tap" template that pre-builds the diagram with utility → meter → tap point with junction dot → main disconnect → main panel, plus the PV array → AC disconnect → tap line. Edit the labels for your specific system size.