NEC Article 690 & Electrical Code
Code requirements for PV source circuits, continuous current factors, conductor ampacity, voltage drop, and conduit fill rules.
- Identify NEC Article 690 as the governing code for PV systems
- Apply the continuous current factor for PV conductor sizing
- Calculate voltage drop for PV circuits
- Describe conductor types and identification requirements
- Explain conduit fill considerations for PV circuits
Lesson 1
NEC Article 690 - PV Systems Overview
The Governing Code
NEC Article 690 is the code article that primarily governs photovoltaic (PV) systems in the National Electrical Code. It covers installation requirements for PV arrays, inverters, conductors, overcurrent protection, disconnects, grounding, and safety systems.
Article 690 supplements the general requirements in NEC Chapters 1 - 4. When Article 690 provides a specific requirement, it takes precedence over the general rule. When Article 690 is silent on a topic, the general NEC rules apply.
Derate Inverter AC Output for Continuous Operation
PV systems produce power continuously during daylight hours, making them continuous loads (or continuous sources). NEC requires that inverter AC output conductors be sized at 125% of the continuous current - the same principle as any continuous load.
NEC Section 690.4(G) - Calculation Rounding
NEC 690.4(G) in the 2026 NEC explicitly allows dropping fractions of an ampere or volt that are less than 0.5 when performing PV system calculations. This rule clarifies a common field practice and prevents over-sizing from rounding up every small fraction.
For example, if a calculation yields 15.3A, this may be rounded down to 15A. If a calculation yields 15.5A or higher, it must be rounded up. This applies to both current and voltage calculations in Article 690.
Rounding Rule - NEC 690.4(G)
Under 2026 NEC Section 690.4(G), fractions of an ampere or volt less than 0.5 may be dropped in PV system calculations. Fractions of 0.5 or greater must still be rounded up. This prevents unnecessary over-sizing from accumulation of small decimal remainders.
2026 NEC - Load Calculation Article Update
The 2026 NEC reorganized the load calculation rules into a new Article 120, replacing the prior Article 220. This affects PV system design because load calculations for the dwelling service are used to determine the available capacity for PV and battery storage additions.
When a PV designer or installer performs load calculations for a dwelling unit to evaluate service capacity or verify compliance with utility interconnection requirements, they must reference Article 120 in the 2026 NEC rather than Article 220. The calculation methodology is carried forward, but the article number and section references change.
Load Calculations: Article 220 (2023 NEC) vs. Article 120 (2026 NEC)
If an exam question or job specification references load calculations, verify which code edition applies. The 2026 NEC moved load calculation requirements from Article 220 to Article 120. The rules are substantively similar - the cross-reference is what changed. For NABCEP exams based on the 2026 NEC, cite Article 120 for load calculations.
NEC Article 690 governs PV system installations. PV systems are treated as continuous sources, requiring conductors sized at 125% of the maximum current. Article 690 supplements general NEC rules. Section 690.4(G) (2026 NEC) allows dropping fractions less than 0.5 in PV calculations. The 2026 NEC moved dwelling load calculation requirements from Article 220 to Article 120 - an important cross-reference change for PV service capacity analysis.