Corverting DC to AC is inefficient. Takes alot of amperage especially if your trying to run multiple devices. Alternators and batteries take a beating. The larger the inverter the worse the problem becomes.
If you’re talking about when parked for a few days. The one I have draws a couple amps even when it’s turned off. I unhook the ground if parking for more than a few days.
If you have a apu and leave it on standby, that’s draining the batteries also.