Calculation Methodology

Calculation engines are pure TypeScript modules. They do not read from a database, call an API, or use browser state to decide a result.

Each result carries the governing constraint and the factors applied, so a user can see whether load, derating, termination temperature, overcurrent protection, fill, or voltage drop decided the answer.

The 2023 edition is the default because it is the newest edition represented in the current data layer, but the user-facing selector is free and must match the edition enforced by the AHJ.

Most encoded numeric tables are shared across 2017, 2020 and 2023 pending official verification. Dwelling EVSE load is edition-sensitive because the 7200 VA minimum is treated as a 2023 rule until reviewed against the official source.

The public implementation uses Chapter 9 Table 8 DC resistance. The unverified Table 9 impedance path is not shipped in the public calculator until the impedance dataset is verified cell by cell.

The 3 percent and 5 percent figures are treated as design recommendations from informational notes, not as a universal code violation.

Public pages can be indexed, but launch claims remain blocked until the underlying datasets are verified against a legitimate NEC copy and the editorial reviewer is named.

Local amendments and AHJ decisions can supersede the published model, so every result remains educational and must be checked against project-specific requirements.