DC vs AC disconnects in solar

Disconnects are the switches that let a person safely isolate part of a solar system. A PV system has both DC and AC sides, and each needs the right kind of disconnect in the right place. Here is where they go, how they are rated, and why the distinction matters.

Two sides, two switches

A grid-tied system produces DC at the array and converts it to AC at the inverter. That split defines the two disconnects:

• DC disconnect — isolates the conductors between the array (and any combiner) and the inverter. Many string inverters have one integrated on the unit.
• AC disconnect — isolates the conductors between the inverter output and the service or main panel. This is the one utilities most often require to be accessible and lockable.

Why DC and AC disconnects differ

The physics of arcing is the reason you cannot swap one for the other. AC crosses zero volts many times a second, so an arc naturally extinguishes at each crossing. DC holds a steady voltage, so an arc, once struck, keeps burning. A DC disconnect is specifically rated to break DC current at the array's voltage; an AC-rated switch on the DC side is a safety hazard and a code violation.

Ratings that matter

Load-break is the key feature: a load-break disconnect can be operated under load without damage or danger. A device that is not load-break must only be opened after the circuit is de-energized, which is why utility-facing disconnects are load-break and lockable.

Where each one lives on the one-line

On your three-line diagram the DC disconnect sits between array and inverter, and the AC disconnect sits between inverter and service. Microinverter systems produce AC at the roof, so they typically have no DC disconnect — the rapid-shutdown function handles roof-level isolation instead, and an AC disconnect still isolates the system from the grid.

Labeling and access

A disconnect only does its job if a first responder or electrician can find and operate it. That is why the NEC and most AHJs require durable labels identifying each disconnecting means, its purpose, and the presence of multiple power sources at the service. Placards call out the PV system disconnect, and directory labels at the main service map where everything connects. The switches also have to be reachable and, for the utility-facing AC disconnect, usually within a defined distance of the meter and lockable in the open position. Missing, wrong, or faded labels are one of the most common and most avoidable inspection failures.

Utility and AHJ requirements

Whether a separate AC disconnect is required, and exactly where and how it must be mounted, is set by your utility and AHJ — not by a single national rule. Some utilities mandate a visible lockable disconnect within reach of the meter; others accept the main breaker. This detail shows up on the permit set and is a common rejection point when it is missing or mislabeled.

Confirm both the DC and AC disconnect requirements with your utility and AHJ, and have a licensed electrician or PE review and stamp the final design.

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.