BYD Qin plus 2025 /GBT charging socket

I would think thats normal, the car consumes some power to run the charging electronics, which can be more than 1kW at times.

Even when the car is off ?

Yes, it loses power to multiple things. I'm gonna give you a list because I'm bored. 1. Resistive losses in cable, cables are often at least 5m long so some resistance there, especially at high current(relatively speaking compared to like a lightbulb or a laptop charger). 2. Contactor contamination, not all plugs are perfectly smooth and microscopic connector gaps cause tiny voltage drops 3. The biggest one, AC to HV DC, the energy is lost to the MOSFETs cleaning up the half sine wave close to a thousand times a second before the rectification is complete, current flowing through the diode bridges causing heat, the boost converters having inductors with constantly changing magnetic fields, causing all the funny magnetic effects 4. Powering systems, cooling fans, pumps, energising solenoids to 'hold open' contacts 5. Battery heat