Model/packages
Khalim Conn-Kowlessar 8e1d30c97d slice S-B4: per-end-use fuel cost (Economy-7 for electric storage)
Splits the single CalculatorInputs.fuel_unit_cost_gbp_per_kwh into three
end-use lines — space_heating, hot_water, other — to match SAP 10.3 §12
which charges different tariffs per end-use on Economy-7 dwellings.

cert→inputs rule: when sap_main_heating_code is in the electric-storage
(401-409), high-heat-retention storage (421-425), or direct-electric
(191-196) ranges, space heating bills at the 7h-low rate (5.5p/kWh)
while hot water + lighting + pumps stay on standard electricity
(13.19p/kWh). All other fuels use a single rate across all three end-
uses.

100-cert parity probe impact:
  MAE   7.53 → 5.72   (-1.81, -24%)
  RMSE 11.60 → 7.58   (-4.02, -35%)
  worst residual -56 → -25 (Semi-detached bungalow)
  within ±10:  85% → 91%

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
2026-05-18 14:18:56 +00:00
..
domain slice S-B4: per-end-use fuel cost (Economy-7 for electric storage) 2026-05-18 14:18:56 +00:00
fetchers added potential file scaffolding: 2026-05-15 10:56:53 +00:00
repos added potential file scaffolding: 2026-05-15 10:56:53 +00:00
utils added potential file scaffolding: 2026-05-15 10:56:53 +00:00
README.md added potential file scaffolding: 2026-05-15 10:56:53 +00:00

Shared packages

Workspace packages consumed by services/*. Each package is its own Python distribution with its own pyproject.toml; services import via the workspace dependency mechanism ({ workspace = true }).

Package Purpose
domain/ Shared domain types — Property, BaselinePerformance, Plan, Scenario, EpcPropertyData, etc. No persistence, no IO, no business logic.
repos/ Persistence layer — one repo per aggregate. Owns the SQL. Depends on domain.
fetchers/ External API clients (gov EPC, Ofgem, Google Solar, etc.). Depend on domain for response shapes.
utils/ Cross-cutting infra — logging, S3, CloudWatch URL builders, SQS task helpers.

Adding a new shared package

Only when a real second consumer materialises. Don't pre-shatter (repos-epc, repos-property, ...) — split when a deployment needs to drop a dep, not before.

See ../ara_backend_design.md §11 for the broader monorepo layout and ../CONTEXT.md for the domain glossary that names the types living in domain/.