Yes, your electric vehicle (EV) will lose some of its charge. Just like any battery-powered device, the battery will drain slowly no matter if it’s in use or not, but how much charge it loses depends on the make and model of the EV.
You can mitigate the battery loss by putting your car into energy save mode or turning off preset features (like air conditioning) that will use a lot of battery. It’s also a good idea to leave the car sitting at less than 100% charge (but no lower than 20%) as leaving it sitting while fully charged can damage the battery.