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5b269f23b6
The CO2 cascade in calculator.py had no PV credit at all
(environmental_section_from_cert had a stale `pv_credit = 0.0` with
the comment "no PV in any Elmhurst fixture", but that helper isn't
called by `calculate_sap_from_inputs` anyway). The full ASHP+PV
cluster therefore over-counted CO2 by +0.16..+0.28 t/yr — the entire
PV CO2 offset was missing.
Wiring (calculator.py):
- New fields: `pv_dwelling_co2_factor_kg_per_kwh: Optional[float]`,
`pv_exported_co2_factor_kg_per_kwh: Optional[float]`.
- CO2 cascade now subtracts:
pv_co2_credit = E_PV,dw × dwelling_CO2_factor
+ E_PV,ex × exported_CO2_factor
when the split + factors are set. None preserves the legacy
zero-credit behaviour for synthetic CalculatorInputs constructions.
Wiring (cert_to_inputs.py):
- New constant: `_PV_EXPORT_FUEL_CODE_TABLE_12 = 60` (SAP 10.2
Table 12 code 60, "electricity sold to grid, PV") — the EXPORT
factor key per Appendix M1 §6/§7/§8.
- The dwelling CO2 factor is the effective monthly Table 12d Σ
weighted by E_PV,dw,m at code 30 (Standard electricity); the
exported CO2 factor is the same Σ weighted by E_PV,ex,m at
code 60 ("Electricity sold to grid, PV"). Both reuse the
existing `_effective_monthly_co2_factor` helper.
Test impact (CO2 residual cluster, re-pinned in this slice):
Pre-Slice 46 → Post-Slice 46:
- 0330 (no PV): -0.034 → -0.034 (unchanged ✓)
- 0350 (PV + 5 kWh battery): +0.171 → -0.084
- 0380 (PV + 5 kWh battery): +0.279 → -0.054
- 2130 (PV + gas combi): +0.299 → -0.046
- 2225 (PV + 5 kWh battery): +0.263 → -0.071
- 2636 (PV + 5 kWh battery): +0.219 → -0.058
- 3800 (PV + 5 kWh battery): +0.261 → -0.014
- 9285 (PV + 5 kWh battery): +0.157 → -0.098
- 9418 (PV + 5 kWh battery): +0.232 → -0.046
- 9501 (PV, no battery): +0.202 → -0.047
Cluster magnitude dropped 3-5× — over-count flipped to slight
under-count (-0.01..-0.10 vs +0.16..+0.28). The remaining negative
residual is largely the same E_PV-magnitude bug from Slice 45 (PV
is over-credited because the cascade thinks E_PV ≈ 3× the worksheet
value for the 5-kWh-battery cohort). Slice 47 (cost cascade) + Slice
S0380.48 (E_PV magnitude audit) will close the cluster further.
Chain tests still <1e-4 — CO2 cascade isn't gated by the chain
tests' SAP-rating-vs-worksheet assertions.
Test suite: 763 pass + 0 fail. Pyright net-zero per touched file
(calculator.py 0/0; cert_to_inputs.py 34/34; test_golden_fixtures.py 1/1).
Spec citations:
- SAP 10.2 specification Appendix M1 §7 (p.94) — PV CO2 credit split.
- SAP 10.2 Table 12d (p.194) code 60 — monthly CO2 factor for
"electricity sold to grid, PV" (already in `tables/table_12.py`).
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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| .. | ||
| addresses | ||
| sap10_calculator | ||
| sap10_ml | ||
| tasks | ||
| postcode.py | ||