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22612a19eb
Slice 3 of ADR-0025 costing. When the dwelling has a reusable wet system, _distribution charges a power-flush (168) plus _REUSE_DISTRIBUTION_FRACTION (0.5) of the full radiator band -- a documented stand-in for partial radiator upsizing at ASHP flow temps, the headline uncertainty in the model. Without a wet system the full new distribution is priced. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
86 lines
3.6 KiB
Python
86 lines
3.6 KiB
Python
"""Behaviour of `Products.ashp_bundle_cost` — the composite, per-dwelling ASHP
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bundle cost (ADR-0025). Pure catalogue math: given a typed `AshpCostInputs` it
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selects and sums the applicable Southern Housing rate lines (decommission +
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heat pump + cylinder + distribution) into a `Cost`, carrying the separate ASHP
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contingency. No EpcPropertyData / calculator — the dwelling interpretation that
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produces the inputs lives in the modelling layer.
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Costs are pinned against the real Southern Housing Group rate sheet, so the
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totals are exact (delta <= 1e-9), mirroring the cascade-pin philosophy.
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"""
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from domain.modelling.products import (
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AshpCostInputs,
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AshpExistingSystem,
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Products,
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)
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from domain.modelling.recommendation import Cost
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def test_ashp_bundle_cost_composes_an_electric_storage_full_distribution_dwelling() -> None:
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# Arrange — a small electric-storage dwelling: no reusable wet system, so a
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# full new wet distribution is priced. 4 kW design heat loss (smallest pump
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# band), 7 radiators.
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products = Products()
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inputs = AshpCostInputs(
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existing_system=AshpExistingSystem.ELECTRIC_STORAGE,
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is_small_property=True,
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design_heat_loss_kw=4.0,
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radiator_count=7,
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has_reusable_wet_system=False,
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)
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# Act
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cost: Cost = products.ashp_bundle_cost(inputs)
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# Assert — decommission 570 + pump 9720 + cylinder 2382.60 + distribution
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# (7 rads) 3618 = 16290.60, with the separate 25% ASHP contingency.
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assert abs(cost.total - 16290.60) <= 1e-9
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assert abs(cost.contingency_rate - 0.25) <= 1e-9
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def _large_no_reuse(system: AshpExistingSystem) -> AshpCostInputs:
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"""A large dwelling, 8 kW band, 8 radiators, no reusable wet system — so the
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only thing varying with ``system`` is the decommission line."""
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return AshpCostInputs(
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existing_system=system,
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is_small_property=False,
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design_heat_loss_kw=8.0,
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radiator_count=8,
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has_reusable_wet_system=False,
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)
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def test_decommission_cost_varies_by_existing_system() -> None:
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# Arrange — common: pump (8 kW) 9840 + cylinder 2382.60 + distribution (8
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# rads) 4152 = 16374.60; only decommission differs by system.
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products = Products()
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common = 16374.60
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# Act / Assert — gas and oil are flat 720; LPG 960; electric-storage large
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# 840 (small 570 is pinned by the tracer above).
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assert abs(products.ashp_bundle_cost(_large_no_reuse(AshpExistingSystem.GAS)).total - (common + 720.0)) <= 1e-9
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assert abs(products.ashp_bundle_cost(_large_no_reuse(AshpExistingSystem.OIL)).total - (common + 720.0)) <= 1e-9
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assert abs(products.ashp_bundle_cost(_large_no_reuse(AshpExistingSystem.LPG)).total - (common + 960.0)) <= 1e-9
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assert abs(products.ashp_bundle_cost(_large_no_reuse(AshpExistingSystem.ELECTRIC_STORAGE)).total - (common + 840.0)) <= 1e-9
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def test_reusable_wet_system_prices_a_flush_plus_half_the_distribution() -> None:
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# Arrange — a gas dwelling whose wet system is reusable: instead of a full
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# new distribution, the ASHP pays a power-flush plus half the radiator band
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# (a documented estimate for partial radiator upsizing — ADR-0025).
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products = Products()
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inputs = AshpCostInputs(
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existing_system=AshpExistingSystem.GAS,
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is_small_property=False,
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design_heat_loss_kw=8.0,
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radiator_count=8,
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has_reusable_wet_system=True,
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)
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# Act
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cost: Cost = products.ashp_bundle_cost(inputs)
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# Assert — decommission 720 + pump 9840 + cylinder 2382.60 + distribution
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# (flush 168 + 0.5 x 4152 = 2244) = 15186.60.
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assert abs(cost.total - 15186.60) <= 1e-9
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