Yes, if you left the lights on, that can kill the battery. But if the battery was the original one and not recently replaced it probably was at the end of its life anyway. Sometimes if you turn off the light switch and wait awhile the battery will regenerate enough to get the vehicle started, but then you need to drive directly to a place to get the battery replaced instead of taking your changes.
If the lights were on when you locked it then it will be the lights, a glove box light can nearly drain a battery overnight.
Regarding towing the best bet would be to get the drive wheels (Should be front) off the ground, or use jump lead just to even put it in neutral.
I sure hope this is not the hybrid model. If the issue is the hybrid batteries you have big bucks about to be needed to replace them. These batteries are prone to an inability to recharge if drained fully!
If the battery is the original, six years old, it is entitled to die. Buy a good battery such as Varta or Bosch and it will last.
I got a "new" car about a month ago (2008 Prius). I tried to drive it yesterday and, well, the battery was dead. The regular car battery. I couldn't use the fob to unlock it and of course it wouldn't turn on when I tried to start it.
All my life I've had cars with automatic lights so I never had this problem. Of course, being so used to that I didn't realize it would drain my battery to leave them "on" (because when I get out of the car and close the door they shut off, but they're not labeled as automatic).
That's probably why it died, right? Seems weird to me, though, that my previous 2006 Camry had automatic lights yet my newer, more technologically advanced Prius doesn't...
Out of curiosity, how do you take a Prius out of gear to tow it since the shift is electric? Not required for the 10 pts just wondering.
