Voltage Drop Code Comparison
All three codes care about voltage drop for the same underlying reason, but the exact limits and how they are applied are not identical. Here is the comparison.
Every electrical code cares about voltage drop for the same physical reason: a cable that's technically within its current rating can still deliver a load-damaging, energy-wasting voltage below what the load needs if it's run too far on too thin a conductor. But the exact limits, and how strictly they're enforced, differ across the three codes OhmWorks covers.
| Code | Typical guidance | Enforcement style |
|---|---|---|
| PEC (Philippines) | Around 3% for a branch circuit, up to roughly 5% total from service to the farthest outlet | Code requirement |
| AS/NZS 3000 / 3008 | Around 5% under normal conditions, tighter limits for some circuit types | Code requirement, calculated from AS/NZS 3008.1.1 resistance data |
| NEC | 3% branch circuit / 5% combined, per the NEC's own informational notes | Recommendation (FPN/Informational Note), not a hard rule — though many local jurisdictions and utilities enforce it as one |
That NEC distinction trips people up: the National Electrical Code frames its voltage drop figures as recommended practice rather than a strict numbered requirement the way ampacity tables are. In practice, treat it as a real limit anyway — a "recommendation" that a permitting authority or utility has adopted as policy behaves exactly like a requirement on your project.
Across all three codes, PV/solar DC circuits are typically held to a tighter limit than general AC circuits — often 1–3% rather than 3–5%. A DC string operates at that voltage drop every single sunny hour of every single day for the system's entire lifespan, so even a small percentage compounds into real lost energy production over 20+ years.
If you're designing to more than one code — a Philippine EPC contractor building to an imported NEC-based spec, for example — never assume the percentage limit from one code transfers directly to another. Confirm which standard actually governs the project, and size to that standard's specific limit.
OhmWorks applies each code's own voltage drop limit automatically depending on which tab you're using — see it in action in the Voltage Drop calculators under PEC, AS/NZS, and NEC.