Where energy goes
Energy is consumed by the onboard charger, battery thermal management, cable resistance, power electronics, and supporting vehicle systems. Loss varies with vehicle, charger, temperature, charging power, and state of charge.
Use measurement when possible
Compare energy reported by the charger or a suitable circuit meter with the battery energy added over the same session. Vehicle dashboard percentages are rounded, so multiple sessions produce a better estimate than one.
Keep the assumption visible
PowerCost Lab exposes charging loss rather than burying it. If you lack measurements, use a planning assumption and test a range. Treat the result as an estimate, not a billing guarantee.
Run your own scenario