A German day is not 24 hours
23 hours each spring, 25 each autumn. A completeness check on a hard-coded 96 quarter-hours raises a false alarm every March and hides a four-interval gap every October.
German energy metering, correct by construction
The open, checkable reference for German energy-metering quantities: every number traces to a published clause, every quoted passage is checked against the PDF. Validation and Ersatzwertbildung, billing quantities and § 14a Modul 3 registers, gas, heat, grid, allocation and EEG — on a calendar where a day has 23, 24 or 25 hours and a Gastag starts at 06:00.
Zero I/O No async No clock Exact decimals
cargo add meteringThree things it gets right that are easy to get wrong
The meter counts, it does not measure intervals
Since June 2025 the gateway delivers a Zählerstandsgang and the Messstellenbetreiber differences it into the Lastgang. Register wraps, implausible jumps and meter exchanges all live at that boundary.
Every citation is checked
Every quoted German passage is matched against the published PDF. Where a source is paywalled or leaves a choice open — G 685's final rounding, the Blindarbeit Freigrenze — the value is a parameter, not an assertion.
What using it looks like
use metering::prelude::*;
use time::{Duration, macros::date};
// The autumn Liefertag is 25 hours: 100 quarter-hours, not 96.
let day = DayBoundary::Strom.day(date!(2026 - 10 - 25)).unwrap();
let slots = (0..100)
.map(|i| MeterInterval::quarter_hour(day.start() + Duration::minutes(15 * i), dec!(0.25), QualityFlag::Measured))
.collect::<Result<Vec<_>, _>>()
.unwrap();
let series = Series::new(Resolution::QUARTER_HOUR, DayBoundary::Strom, slots).unwrap();
let period = aggregate(&series, day).unwrap();
assert_eq!(period.arbeitsmenge, dec!(25)); // exact Decimal kWh
assert_eq!(period.spitzenleistung_kw, Some(dec!(1))); // kW, from kWh × 3600 ÷ s
assert_eq!(period.coverage.pct(), Some(dec!(100))); // against the declared day
What it deliberately does not do
| Not here | Why | Where instead |
|---|---|---|
| Money — prices, Netzentgelte, Umlagen, invoices | the output is kWh, m³ and kW | your billing layer |
| EDIFACT / XML market messages | parsing a MSCONS is not arithmetic | mako |
| Fristen — counting Werktage to a deadline | a process-engine concern | your process engine |
| SMGW certificates and device inventory | PKI and asset tracking, not quantities | your device management |