It also depends on what you set it on.
Try running it on “Hi” (i don’t know what the equivalent is – just the heater knob all the way to 11), curious if it’d do it. It certainly should pull more than is available trough a 13A socket, around 4-8kw regardless of whether or not you have a heat pump (in a pure EV), since that obviously doesn’t do anything in a stationary/cold car. You can get around that by “not demanding” a lot of the heating/preconditioning, but as i said, we need the car properly warm in winter.