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Slice 2 of Bill Derivation. BillDerivation(fuel_rates).derive(breakdown) takes a delivered-energy breakdown (per-section EnergyLine(section, fuel, kwh) + exported_kwh) and produces a Bill: per-section kWh + cost, standing charges, SEG credit, and total. - Each end-use line billed at its fuel's unit rate. - Standing charge added ONCE per distinct fuel used (a meter, not an end use); off-gas fuels carry 0 so contribute nothing — no metered/unmetered special case. - SEG export credit subtracted. - Deterministic (ADR-0006); raises UnpricedFuel (via FuelRates) on an unpriced fuel (e.g. heat network) rather than billing at a wrong default. Pure domain — no calculator dependency; the SapResult->EnergyBreakdown adapter is slice 3. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
58 lines
1.5 KiB
Python
58 lines
1.5 KiB
Python
from __future__ import annotations
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from collections.abc import Mapping, Sequence
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from dataclasses import dataclass
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from enum import Enum
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from domain.fuel_rates.fuel import Fuel
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class BillSection(Enum):
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"""A user-meaningful slice of the annual energy bill — the calculator's raw
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end uses folded into the sections the UI shows (ADR-0014)."""
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HEATING = "HEATING"
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HOT_WATER = "HOT_WATER"
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LIGHTING = "LIGHTING"
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APPLIANCES = "APPLIANCES"
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COOKING = "COOKING"
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PUMPS_FANS = "PUMPS_FANS"
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@dataclass(frozen=True)
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class EnergyLine:
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"""One section's delivered energy on one fuel. A section may have more than
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one line (e.g. gas main heating + electric secondary heating)."""
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section: BillSection
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fuel: Fuel
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kwh: float
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@dataclass(frozen=True)
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class EnergyBreakdown:
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"""A Property's delivered energy per end use, the input to Bill Derivation —
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produced from SAP10 Calculation in a later slice. ``exported_kwh`` is PV
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generation exported to the grid, credited at the SEG rate."""
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lines: Sequence[EnergyLine]
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exported_kwh: float = 0.0
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@dataclass(frozen=True)
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class BillSectionCost:
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"""One section's rolled-up delivered kWh and annual cost (£)."""
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kwh: float
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cost_gbp: float
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@dataclass(frozen=True)
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class Bill:
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"""A Property's annual energy bill, composed per section plus the per-meter
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standing charges and the SEG export credit, and the total (ADR-0014)."""
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sections: Mapping[BillSection, BillSectionCost]
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standing_charges_gbp: float
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seg_credit_gbp: float
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total_gbp: float
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