A KPI is a derived metric configured on a machine's firmware. Each KPI has a type (an identifier like energy-consumption, uptime), a variable_type that determines its semantics, and a unit of measure. variable_type: metrics What it represents: Numeric metric multiplied by a coefficient (e.g. instantaneous power → energy). Coefficient meaning: Single multiplier applied to every data point. ──────────────────────────────────────── variable_type: states What it represents: Time spent in one or more state values (e.g. compressor=on, door=open). Coefficient meaning: Per-state weight applied to the duration. Example: compressor=on with coefficient 1 means 1 kW while on, so 5 hours = 5 kWh.