Free tool
Will my panel accept a solar inverter?
The busbar rule, in one screen. Enter the panel, the main breaker and the
inverter, and see the largest system the panel takes without being replaced.
Use the continuous AC output of the inverter from
its label, not the size of the array in DC watts.
is the largest inverter this panel accepts
Enter a system
The rule. Where a panel is fed by a main breaker at one end and
the inverter breaker sits at the opposite end, the main breaker and the inverter breaker
together may not exceed 120 percent of the busbar rating. NEC 705.12. The inverter breaker
itself is sized at 125 percent of the continuous output current of the inverter.
Three conditions that come with it. The inverter breaker has to
be at the opposite end of the busbar from the main, the panel needs a permanent label saying
so, and a centre fed panelboard cannot use this allowance at all.
If it does not fit. The usual options are a smaller main
breaker, which is often possible because most services are nowhere near loaded, a supply side
connection ahead of the main, or a new panel. An electrician decides which one is right.
What this does not do. It does not check conductor sizes, the utility
interconnection agreement, rapid shutdown, or any local amendment. It answers one question:
does the busbar take it.