Each hourly energy snapshot records the price, and the energy used until the
next one is costed at it. Prints and the Statistics energy cost follow the
price over time instead of applying one price after the fact. The price can
come from a Home Assistant sensor, read hourly and at print start and end.
Energy multipliers now accept any value above zero, for plugs that report
watt-seconds.
The Statistics page reported "Gesamt" (All Time) kWh correctly but showed
zero for Today/Week/Month in total-consumption mode. Two bugs drove it:
1. The starting plug counter was kept in an in-memory dict
`_print_energy_start` that was lost on any backend restart mid-print, so
the per-print `energy_kwh` delta silently never got computed. The stats
endpoint's fallback path `SUM(PrintArchive.energy_kwh)` therefore summed
to zero for users running in total mode.
2. Total-consumption mode has no per-print delta by design — it includes
idle/preheat/standby — so the fallback to archive rows was the wrong
strategy even when the data existed.
Fix, in two parts:
- Persist `energy_start_kwh` on the archive row and read it back from a
fresh session at print end. Deletes `_print_energy_start` and its 5
call sites, replacing them with a single `_record_energy_start()` helper.
Per-print tracking is now restart-resilient regardless of tracking mode.
- Add hourly `smart_plug_energy_snapshots` table + `_snapshot_loop()` in
SmartPlugManager. Rewrote the `/archives/stats` energy branch as
`_sum_snapshot_deltas()` which computes per-plug
`max(0, last-in-range - baseline)` where baseline is the latest snapshot
at or before the range start, falling back to the earliest-ever snapshot
and signalling `energy_data_warming_up` when no pre-range baseline
exists (fresh upgrade). MQTT plugs are skipped from snapshots since they
only report "today" and have no lifetime counter.
Frontend: QuickStatsWidget renders an AlertTriangle next to Energy Used /
Energy Cost with a tooltip when `energy_data_warming_up` is true, so the
"low values right after upgrading" situation is explained in-product.
Fully localised across 7 UI languages.
Tests: new backend unit tests cover the snapshot delta arithmetic
(baseline/endpoint, counter reset clamp, multi-plug, warming-up fallback,
endpoint windowing), per-print restart resilience via expunge_all, and the
snapshot task lifecycle (start idempotent, stop cancels). Frontend tests
assert the warning icon appears only when the flag is set and only on the
energy tiles.
Docs: updated `CHANGELOG.md`, `README.md`, wiki `features/energy.md`,
wiki `features/statistics.md`, and website `features.html` with the new
behaviour and warming-up explanation.
maziggy