Hide the key (fob)

I would think it just experienced unnecessary wear and tear, but nothing harmful.

I thought there are various clues to indicate the Prius is still on.

 

The only real issue I could see is how easily the car can walk away with unlocked doors and an engine that's on

 

Went to a music festival with a friend. Left my car parked in her garage. It was three days later when her husband happened to be in the garage when engine was running. He called our motel and told her. I told him how to shut it off. When I returned to my Prius a few days later I still had nearly a full tank of gas and battery was fine. Her husband (an anti-prius guy) just knew I was going to have a dead battery. I tried to assure him over the phone that all would be well. Sheesh!

 

No harm would be done. You would lower your average fuel economy on that tank and would have wasted perhaps a gallon or two of fuel. In a closed garage it could be dangerous due to the possibility of CO gas being generated. And as posted above the car could be stolen. That's about it.

 

when you shut the door with the car on, it beeps at you three times. pretty hard to miss.

 

if you make a habit of locking the doors, it won't let you unless you turn it off.

 

btw, what does your post have to do with the title?

 

No harm done - the engine would have been off most of that time, just coming on occasionally to maintain the charge on the traction battery.
A number of us here have kept our cars in Ready mode for many hours while using the Prius as an emergency backup supply during electrical outages. My longest run was 54 hours after Hurricane Sandy, during which the car used only about a gallon of gas.​

 

aha!

 

And I heard no audible warning because I had decided to leave my key fob in the cup holder in case her husband needed to move the car for any reason. Which prompts another question: Is there any problem with leaving the fob in the car? I park in my garage and do it all the time, for convenience sake. But it seems I recall some discussion on a problem of some sort in doing this. (I have done it for 11 years, in my 2006, 2010, and 2013 Prii.)

 

If the car is locked and the key is too close to the car, it will use a lot of battery power (mainly in the fob) checking if the key is still close enough to unlock the car. I don't think it keeps this communication up when the car is unlocked, though. But if you notice that your fob battery dies quickly, this could be a reason.

 

If your wife/husband/significant other leaves the car on like this it's best to just explain to him/her that it's a waste of fuel and possibly dangerous (a kid, for example, could take the car for a joyride) "so please be careful in the future". Family harmony is MORE important than a Prius!