Common solar electrical plan-check corrections

Electrical corrections are the most common reason a residential solar permit gets kicked back. Nearly all of them are the same handful of NEC issues, and nearly all are quick to fix once you know what the reviewer is checking. Here are the top electrical rejections and how to clear each.

1. Busbar overload — the 120% rule (NEC 705.12(B))

On a load-side interconnection, main breaker + back-fed solar breaker must not exceed 1.2 × the busbar rating. A 200 A busbar with a 200 A main leaves room for only a 40 A solar breaker. Exceed it and the reviewer corrects it.

Fixes: downsize the main breaker, switch to a supply-side (line-side) tap, or upgrade the busbar. Show the math on the one-line so the reviewer does not have to guess.

2. Conductor and OCPD sizing (NEC 690.8 / 240.6)

The classic miss is skipping the stacked 125% factors (about 1.56 × Isc) or forgetting the temperature and conduit-fill derate on a hot roof — landing on a wire that looks fine but is under-ampacity after derating.

Fix: apply the full 690.8 continuous-current factors and the ambient/fill corrections, then confirm the OCPD and conductor agree. Show the derated ampacity on the drawing.

3. String voltage over the inverter maximum (NEC 690.7)

Cold weather raises a string's open-circuit voltage. If the coldest-expected-temperature Voc exceeds the inverter's max input, the string is corrected.

Fix: re-run the Voc correction at the record-low temperature for the site, not a nominal 25 C, and adjust the string length.

4. Rapid shutdown missing or mislabeled (NEC 690.12)

Reviewers look for an actual device on the one-line — microinverters, DC optimizers, or a listed PV rapid-shutdown system — plus the initiator and the required placard. A note that says "rapid shutdown provided" with no device gets corrected. Our 690.12 explainer covers what qualifies.

5. Grounding and bonding gaps (NEC 250 / 690.47)

Common misses: no grounding electrode system, an undersized grounding electrode conductor or equipment grounding conductor, or missing array bonding.

Fix: show a grounding electrode per 250.50, size the GEC and EGC to the applicable tables, and call out listed bonding hardware for the array.

6. Labels and placards (NEC 705.10 / 690.56)

The service directory/plaque, PV disconnect labels, and rapid-shutdown marking all have to appear on a label schedule. Reviewers check for them explicitly, and a missing label is a correction even when the wiring is perfect.

Why these repeat

None of these are hard to get right — they are just easy to forget on a hand-drawn set. A design that passes the 120% math, sizes conductors after derating, corrects string voltage cold, names its rapid-shutdown device, and carries a full label schedule clears electrical plan check on the first pass far more often. For the deeper rejection list, see why solar permits get rejected.

A design tool cannot guarantee approval, and a licensed electrician or PE must review and stamp the electrical design. But building the set right the first time — using our DIY workflow or the reference library — is how you avoid the correction queue entirely.

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.