I don't know about others, but my 300W unit draws very little power when it is not actively powering a device. It would take days or a week to drain the battery. I once used the unit to run the car radio, and my powerbook at the same time (playing DJ for a party in the woods) and ran my battery down in 6 hours... I have yet to see a power inverter with a power switch.

My 300W unit fit nice and snug between the driver's seat and the transmission hump in my RX-7 (a small two seater) Unless one knew it was there it was unnoticeable. Most modern cars have direct battery power to the cigarette lighter. This is not switched off. A switch could be added without too much effort.

=B-)

To answer your question, Yes, the inverter shuts off when the ignition is turned off. It will run, as all electrical items in the car will also run, as long as the key in the ignition is switched to On, and the inverter is plugged into the cigarette lighter socket. Don't know if the micro inverter drains the battery when the ignition is off. I doubt that it does. The 175 gets so noisy when it's on (from its internal fan) that I have to turn up the volume of my car stereo and the little green light brightens to indicate that it's operating. Once the power (ignition) is turned off, the inverter won't run an electrical device.

You could call Xantrex and ask the customer rep whether the possibility of a battery drain exists. Me, I just pull the nifty gadget out of the cigarette lighter socket once I'm done and then put it in the glove compartment, if I'm traveling, or I take it with me to my apartment when I get home. Don't need any excuse for a thief to break into my car.