The thesis
Three principles drive every feature decision.
Engine-driven, never hand-drafted
Every output (number, label, diagram, PDF) comes from the same calculation engine. Nothing drifts between the math, the report, and the SLD because they all read the same derived state.
Trace everything
Every result shows the rule reference, formula, substitution, and intermediate value. NEC-220.42 with the literal kVA tier breakdown. Defensible at any AHJ plan review.
Permit-shaped, P.E.-sealed
EEP produces submittal-shaped documents; the licensed engineer seals them. The product respects the boundary — no auto-stamp, no fake authority, no claim to certify designs.
How it actually works
Single source of truth, reactive everywhere.
- 1. Project state. One JSON object holds the whole project — service parameters, panels, loads, feeder overrides. The designer edits any part of it from any UI surface.
- 2.
derive(state)— one pure function. A single pass produces: connected kVA → demand (rule pack) → service OCP → conductor → EGC → feeders → conduit fill → voltage drop → panel schedule → SLD → 26 warnings → compliance summary. - 3. Rule pack. NEC and CEC are first-class citizens. Each rule (e.g. NEC
220.42lighting demand, CEC8-200(a)(i)residential basic) is a code object withappliesTo()andapply(). The engine evaluates the right pack based on projectstandard. - 4. Persistence. Every save creates a versioned snapshot. Restore is a new snapshot, not a rewind — the timeline never moves backward. The change log is immutable by API design.
- 5. Outputs. The permit-shaped report and the standalone SLD both consume the same derived snapshot. They cannot show different numbers.
What EEP will never do
Auto-stamp designs
EEP renders a signature/seal area sized for a P.E. stamp. It will never apply that stamp itself. Sealing is a licensed engineer's act of professional judgment.
Hide an engineer's override
If you override a feeder OCP above the service OCP, the platform flags the violation but keeps your override. We never silently "correct" professional judgment.
Rewrite history
The change log is append-only at the API level. There is no endpoint to delete or modify a logged action — by design, not omission.
Free-tier theatre
The free tier (residential ≤ 300 m²) uses the same engine, same warnings, same PDF, same trace as paid. Free is full-strength, gated only by project size.
Honest about scope
EEP is not a CAD tool, not a power-flow simulator, not an arc-flash incident-energy engine (yet). It is a real-time NEC/CEC compliance workflow with traceable calculations and team review. We do that one thing very well, and document the rest as out-of-scope.