NEC 690 Compliance for Solar Bids (Without Getting Bounced at Inspection)
A solar inspection fail isn't a paperwork problem. It's a 2-3 week schedule slip, a $1,800 re-pull of conductor, and a customer who's now telling neighbors about your install. The fail is preventable at bid time. NEC 690 is published, the gotchas are known, and the bid that prices it correctly the first time keeps the install on schedule.
The four sections that cause most fails
NEC 690.7 — Maximum Voltage. Open-circuit voltage at the coldest expected ambient is the real limit, not the STC rating on the datasheet. A 24-module string of 41.5V modules at 25°C is 996V — well within most string inverters. The same string at -10°C is 1,143V — over the 1,000V limit. Bid the string length the cold math allows, not the warm math.
NEC 690.8 — Conductor Sizing. The continuous-current rating × 1.25 × 1.25 (two safety factors stacked) drives the minimum conductor ampacity. A 12A Imp module × 1.25 × 1.25 = 18.75A minimum conductor ampacity. After temperature and conduit fill derating, that's typically #10 AWG copper, not #12. Bid #10, not #12, and the inspector signs off.
NEC 690.12 — Rapid Shutdown. Any rooftop residential array needs module-level rapid shutdown. Microinverters and DC optimizers both comply. String-only-without-MLPE does not. The bid line item is either microinverters or string-inverter-plus-MLPE. Don't bid a non-compliant system and try to argue it at inspection.
NEC 690.13 — Disconnects. Required AC and DC disconnects, with specific labeling requirements (NEC 690.56 covers signage). A $180 line item missed at bid time is a $400 charge to fix at inspection.
The bid line items
Every NEC 690-compliant residential solar bid carries:
- Modules + microinverters (or string inverter + MLPEs)
- DC + AC disconnects (with code-compliant signage)
- AC combiner / panel modifications if required
- Cold-temperature-correct conductor sizing
- Rapid shutdown initiator + labeling
- Bonding to grounding electrode system per NEC 690.43 + 690.47
- Penetration flashing per IRC for the racking attachments
Each item should appear as a separate line, not folded into a "miscellaneous electrical" allowance. The customer doesn't read your bid line by line, but the inspector does.
How Estimate.Pro handles it
The solar trade template inside Estimate.Pro carries every line item above pre-populated. The conductor sizer pulls the cold-ambient design temperature for the ZIP code and applies the 1.25 × 1.25 rule. The rapid-shutdown topology choice is a single dropdown — microinverter or MLPE string. The bid output reads like a code-compliant submittal package, not a sales sheet.
The bottom line
NEC 690 is published. There's no excuse for an inspection fail on the published sections. Bid the code-compliant scope the first time and the install goes from "bid, install, fail, re-pull, pass" to "bid, install, pass" — 2-3 weeks of schedule and $1,800 of avoidable re-work.