It appears that we have the information we need to do the "€0.8 per kilowatt" format, by formatting the currency value, then using either the unit-specific per pattern, or the generic per pattern to compose.

We also need a format for the unit identifier, eg,

eur-per-kilowatt
or
curr-eur-per-kilowatt

Note: since we currently don’t collect inflection data for currency units, any inflections would not be reflected in the currency. That would be a different ticket.