Data normalisation
Each record is stored exactly as its source published it. Capacity stays in the unit it was quoted in, and prices keep their original currency and price unit — nothing is rewritten on import.
What is normalised is notation, not magnitude: `kwh` becomes `kWh`, a lower-case currency code becomes its ISO form, and dates become ISO format. A number that arrives with a thousands separator, an embedded unit or an ambiguous date is rejected rather than guessed at.
When you filter by capacity, the filter bound is converted between kWh and MWh — an exact factor of 1 000 — and compared against records in their own units. The records themselves are never converted.