Solar & Battery Basics

PV string voltage per 690.7, load-side 120% busbar rule per 705.12(B)(3)(2), inverter output breaker sizing, and battery runtime.

PV string Voc (690.7)

Module Voc (V, STC) Voc temp. coeff. (%/°C) Lowest expected temp Units Modules in series Inverter/MPPT max DC V

120% busbar rule (705.12)

Busbar (A) Main breaker (A) Inverter output (A)

Battery bank

Battery voltage (V) Amp-hours each (Ah) Number of batteries Usable depth of discharge Inverter efficiency Average load (W)

Low-temperature design value: use the ASHRAE Extreme Annual Mean Minimum Design Dry Bulb for the nearest station (690.7(A) informational note). Never assume a value — look up the station for the site. Table 690.7(A) factors (crystalline silicon) are shown for comparison when no coefficient is available. Morningstar Electric LLC installs EG4 inverters and batteries; follow the specific model's installation manual and listing (UL 1741 / UL 9540) for terminal ratings and breaker limits.

Reference only — not engineering, legal, or code-compliance advice. Results are estimates for qualified persons and must be verified against the NEC edition adopted where the work is done (your selected edition), manufacturer instructions, and the local AHJ. Use is subject to the Terms of Use & Disclaimer. — Morningstar Electric LLC