Version rate plans by effective date #46

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opened 2026-07-17 03:09:20 +00:00 by claude-bot · 0 comments

claude-bot commented

2026-07-17 03:09:20 +00:00

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src/lib/rates.js hardcodes one tariff snapshot. Ameren MO rates change ~annually (a ~15.5% PSC case is pending per the spec's caveats). Restructure the rate constants as a dated list ([{effectiveFrom: '2025-06-01', ...rates}]) with lookup by row timestamp in both the hourly and parametric paths, so: historical bill reconciliation prices old months at old rates; projections can model the pending increase as a dated step instead of only a smooth escalation %; and a rate update is an append, not a rewrite. Bump CALCULATION_FORMULA_VERSION on schema change so caches invalidate once.

Rationale: the spec froze a single tariff snapshot; nothing in the roadmap contemplated the tariff itself changing, though it changes roughly annually in Missouri. Without this, every future rate edit silently rewrites history.

Acceptance criteria

Rate lookup is date-aware in both engines
Adding a future-dated tariff changes projections but not historical months
Reconciliation of a pre-change bill uses the tariff in force then

Relations: relates to #16 (formula-version/caching interplay), #24 (reconciliation correctness)

(Audit finding F-27, 2026-07-16 — feature, ranked #2)

`src/lib/rates.js` hardcodes one tariff snapshot. Ameren MO rates change ~annually (a ~15.5% PSC case is pending per the spec's caveats). Restructure the rate constants as a dated list (`[{effectiveFrom: '2025-06-01', ...rates}]`) with lookup by row timestamp in both the hourly and parametric paths, so: historical bill reconciliation prices old months at old rates; projections can model the pending increase as a dated step instead of only a smooth escalation %; and a rate update is an append, not a rewrite. Bump CALCULATION_FORMULA_VERSION on schema change so caches invalidate once. Rationale: the spec froze a single tariff snapshot; nothing in the roadmap contemplated the tariff itself changing, though it changes roughly annually in Missouri. Without this, every future rate edit silently rewrites history. **Acceptance criteria** - [ ] Rate lookup is date-aware in both engines - [ ] Adding a future-dated tariff changes projections but not historical months - [ ] Reconciliation of a pre-change bill uses the tariff in force then **Relations:** relates to #16 (formula-version/caching interplay), #24 (reconciliation correctness) *(Audit finding F-27, 2026-07-16 — feature, ranked #2)*

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2026-07-17 03:12:01 +00:00