metering

German energy metering domain library — interval types, gas conversion, billing period aggregation, SLP/RLM/iMSys classification, and Hampel-filter quality scoring.

metering is the pure domain library used by edmd for all metering arithmetic. It has no I/O, no async, and no floating-point money.

Design constraints

Constraint	Detail
No I/O	All inputs are passed as arguments.
No async	Synchronous throughout.
No float money	All energy amounts use `rust_decimal`.
Deterministic	Same inputs always produce the same output.

Core types

`MeterInterval`

A single timestamped energy reading:

pub struct MeterInterval {
    pub period_start: OffsetDateTime,
    pub period_end: OffsetDateTime,
    pub value_kwh: Decimal,
    pub quality: QualityFlag,
}

`Sparte`

pub enum Sparte { Strom, Gas }

`QualityFlag`

Measured, Substituted, Estimated, Invalid — mapped to MSCONS/UTILTS Datenqualitätskennzeichen.

Gas conversion: m³ → kWh_Hs

pub fn gas_m3_to_kwh_hs(
    m3: Decimal,
    brennwert_kwh_m3: Decimal,
    zustandszahl: Decimal,
) -> Decimal

Implements the Brennwertkorrektur formula per §24 GasGVV / DVGW G 685:

$$kWh_{Hs} = m^3 \times z \times H_s$$

Billing period aggregation

aggregate computes a BillingPeriodAggregate from a slice of MeterIntervals:

let agg = aggregate(&intervals, &AggregationConfig::rlm_strom())?;
println!("kWh HT: {}", agg.kwh_ht);
println!("kWh NT: {}", agg.kwh_nt);
println!("Spitzenlast: {:?} kW", agg.spitzenleistung_kw);

`AggregationConfig` presets

Preset	Messtyp	Split
`rlm_strom()`	RLM	Spitzenleistung §2 Nr. 17 MessZV + HT/NT split
`slp_strom()`	SLP	HT/NT split (no Spitzenleistung)
`rlm_zweitarif()`	RLM	Custom HT/NT window
`gas()`	Gas	Single total (m³ → kWh_Hs, no tariff split)

SLP/RLM/iMSys classification

pub fn classify_messtyp(
    malo: &MaloId,
    jahresverbrauch_kwh: Decimal,
    sparte: Sparte,
) -> Messtyp

`Messtyp`	Criteria	Basis
`Slp`	< 100 MWh/a (Strom) or < 1.500 MWh/a (Gas)	§3 MessZV
`Rlm`	≥ 100 MWh/a (Strom) or ≥ 1.500 MWh/a (Gas)	§4 MessZV
`Imsys`	Pflichteinbau iMSys (§41a EnWG)	§41a EnWG

Mehr-/Mindermengensaldo

pub fn compute_imbalance(
    forecast_kwh: Decimal,
    actual_kwh: Decimal,
) -> ImbalanceResult

ImbalanceResult contains delta_kwh and delta_pct. Positive = Mehrmenge (actual > forecast); negative = Mindermenge. Basis: §27 MessZV.

Hampel-filter quality scoring

score_intervals runs a Hampel filter over a time-ordered slice of intervals and returns per-interval QualityGrades:

pub fn score_intervals(
    intervals: &[MeterInterval],
    window_k: usize,   // half-window size (default: 3)
    threshold: f64,    // MAD threshold in sigma units (default: 3.0)
) -> Vec<QualityGrade>

`QualityGrade`

Grade	Meaning	Effect in `edmd`
`A`	Clean — within threshold	Billing proceeds normally
`B`	Slightly suspicious	Logged; billing proceeds
`C`	Likely outlier	`de.edmd.reading.quality.warning` CloudEvent emitted
`F`	Severe outlier / substituted	Billing run blocked; operator alert

hampel_filter is also exposed as a low-level primitive that returns raw outlier indices.

§17 MessZV substitute value generation

When meter readings are missing or faulty, the MSB must supply substitute values before billing. metering implements all four methods from §17 MessZV and BDEW practice.

Quick usage

use metering::{fill_gaps, fill_gaps_with_config, FillGapsConfig, SubstituteMethod};

// Automatic method selection (linear for short gaps, carry-forward for long)
let filled = fill_gaps(&intervals, 900, period_from, period_to);

// Prior-period averaging per §17 Abs. 2 MessZV (same time-slot, prior week)
let prior_week: Vec<MeterInterval> = fetch_prior_week(&malo_id);
let filled = fill_gaps_with_config(
    &intervals, 900, period_from, period_to,
    &FillGapsConfig::prior_period(prior_week),
);

`SubstituteMethod` variants

Variant	When to use	BDEW recommendation
`LinearInterpolation`	Short gaps (≤ 3 intervals) with surrounding data	Primary for RLM/iMSys
`PriorPeriodAverage`	Longer gaps; same time-slot from prior reference week	Biomass, industrial load
`ZeroFill`	Documented plant shutdown — affirmative zero only	Outage with evidence
`LastValueCarryForward`	Conservative fallback when no context available	SLP, default for longer gaps

`FillGapsConfig`

pub struct FillGapsConfig {
    pub method: SubstituteMethod,            // default: LinearInterpolation
    pub prior_period_intervals: Vec<MeterInterval>, // for PriorPeriodAverage
    pub short_gap_threshold: usize,          // default: 3 (auto-linear below this)
}

FillGapsConfig::prior_period(prior_week_intervals) and FillGapsConfig::zero_fill() are convenience constructors.

Filled intervals carry quality = QualityFlag::Substituted (billable per §17 MessZV Abs. 1).

Feature flags

Flag	Effect
`serde`	Derive `Serialize`/`Deserialize` on all public types

Testing

cargo test -p metering --all-features

37 tests covering gas conversion, aggregation (RLM/SLP/Gas), Messtyp classification, imbalance arithmetic, Hampel filter edge cases, and §17 MessZV substitute value generation (all four methods including PriorPeriodAverage).

Regulatory basis

§3, §4 MessZV — SLP/RLM classification thresholds
§2 Nr. 17 MessZV — Spitzenleistung definition for RLM
§17 MessZV — Ersatzwertbildung (substitute value generation)
§27 MessZV — Mehr-/Mindermengensaldo
§24 GasGVV / DVGW G 685 — Gas Brennwertkorrektur
§41a EnWG — 15-Minuten-Lastgang and iMSys Pflichteinbau

metering 0.10.0