EV Charger Branch, Feeder & Service Calculator

Size branch circuits, feeders, and service entrances for EVSE installations under NEC 625 — supporting Level 1, Level 2, and DC Fast charging with demand factor application and multi-unit feeder aggregation.

AVAILABLEAUTOMATED CHECKS ONLYSTANDARDS-AWAREINTERMEDIATENECWHAT DO THESE STATUSES MEAN?

NEC • ART. 625L1 / L2 / DC FASTNEC 2017 / 2020FEEDER AGGREGATION

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Overview

EV charging infrastructure is one of the fastest-growing NEC design challenges, and Article 625 introduces continuous-load factors, demand factor options, and load-management system provisions that are easy to misapply. This calculator works through the complete circuit design hierarchy: branch circuit conductor and OCPD sizing for individual EVSE units, feeder aggregation with demand factors for multiple units, and service entrance sizing. It supports Level 1 (120 V), Level 2 (208 V / 240 V single-phase, 208 V / 480 V three-phase), and DC Fast concepts across NEC 2017 and 2020 editions. Conductor material (aluminum or copper) and temperature rating (60°C, 75°C, or 90°C) are selectable. The Trace tab shows step-by-step NEC calculation logic so every result is traceable to a code section. A Challenge mode presents EVSE design problems for self-assessment. NEC Reference panels are provided for Articles 625, 220, and 310. Designed for engineers and contractors sizing charging infrastructure for commercial and industrial occupancies.

App preview

A live look at the app you'll launch — every control on the left drives the visualizations on the right in real time.

Inside the lab

Example data — not a real field report

Overview tab with EVSE inputs, charging level selector, and demand factor controls — Overview · Set EVSE level, voltage, phase, quantity, conductor material, and temperature rating — then apply NEC 625 continuous-load and demand factor options in one panel.

Results tab showing branch, feeder, and service sizing with conductor and OCPD picks — Results · Branch circuit, feeder, and service entrance sizing rolled up side by side, with conductor size, OCPD rating, and required ampacity for each level of the hierarchy.

Calc Trace tab showing step-by-step NEC calculation logic — Calc Trace · Every value cross-referenced to the NEC section that produced it — 625.42 continuous load, 220.86 demand factors, 310.16 ampacity — so results are auditable.

Code Logic tab with NEC 625, 220, and 310 reference panels — Code Logic · Article 625, 220, and 310 reference panels explain when demand factors are allowed, how load-managed EVSE changes the math, and NEC 2017 vs. 2020 differences.

Learn tab with EVSE background and design guidance — Learn · Background on Level 1 / Level 2 / DC Fast charging, continuous-load treatment, and how load-management systems affect feeder and service sizing decisions.

Design Challenge tab with graded EVSE sizing problems — Design Challenge · Basic, intermediate, and advanced EVSE sizing problems with graded answers — a quick self-check before you commit sizing to a real project.

What you'll do

01Apply the NEC Article 625 continuous-load factor to EVSE branch circuit sizing
02Select conductor size and OCPD rating for Level 1, Level 2, and DC Fast EVSE circuits
03Aggregate multiple EVSE loads with demand factors to size a common feeder
04Distinguish load-managed EVSE systems and explain how they affect feeder and service sizing
05Compare NEC 2017 vs. 2020 Article 625 provisions and identify changes relevant to EVSE design
06Trace every sizing step to the applicable NEC section using the Calculation Trace tab

What this lab is not

Not a design document, stamped calculation, or approval record.
Not a substitute for engineering analysis by a licensed professional.
Not a reproduction of NEC tables — values are computed and cited, and you must verify against the code edition enforced in your jurisdiction.
Not connected to live equipment and not a safety device.

Calculation basis

References NEC. Results are computed from the entered inputs and cited back to the referencing clause or table number — no code text or table is reproduced verbatim.

Simplifying assumptions are stated in the lab itself; where a model is intentionally conceptual, the lab says so rather than implying study-grade accuracy.

Standards basis: Standards-aware. Validation state: Automated checks only (last checked 2026-08-15).