Guides for solar installers
Code, permitting and interconnection, written for the people who design and file the sets.
What goes in a solar permit plan set
A sheet-by-sheet checklist: cover, site plan, roof plan and fire pathways, structural details, line diagram, calculations, labels and spec sheets.
The 120% rule for solar, explained
What NEC 705.12 says, the math with a worked 200 A example, a quick-reference table for common panels, and what to do when a panel fails.
Supply-side taps: NEC 705.11, explained
When a line-side tap is the right fix, conductor sizes, overcurrent protection location by edition, and the utility.
Solar rapid shutdown: NEC 690.12, explained
The array boundary, 30 V and 80 V limits, UL 3741, the initiation device and labels, edition by edition.
String voltage at the record low: NEC 690.7
The temperature coefficient formula, which low to use, the 600 V dwelling limit, and the hot-weather minimum.
Home battery permits: IRC R328, explained
Where a battery can go, the 20 kWh and 40/80 kWh limits, spacing, detection, vehicle barriers and what to show on the set.
SolarAPP+: how instant solar permitting works
How the automated permit tool works for installers, what it covers, where it’s available by state and what it saves.
How to answer a solar plan-check correction letter
Sorting the comments, the corrections that come up most, revising the set and writing the response letter.