Does overnighting in a Prius weaken the battery or motor?

Assuming that you keep your Prius in "Ready" mode so that the ICE runs periodically to maintain the traction battery, the only negative effect on the battery is a few extra recharge cycles. This is a much lower stress than driving in stop and go traffic,

JeffD

 

Make sure you keep the traction battery cooling vents clear and unobstructed and a full tank of gasoline. You may not be able to make it to a gas station in the morning. Crack at least one of your windows for proper ventilation. Don't be surprised by the accumulated moisture in your cabin in the morning.
As far as heating goes, there are really cheap (around $100), 12vdc diesel/kerosene heaters out there. It's a bit bulky and I would run it outside my car anyways - using the remote and a heating tube into the car window. They usually last more than 10 hours on a few liters of fuel.

Happy trails and merry x-mas...

 

lots of people have been overnighting in prius for decades with no measurable detrimental effects

 

Every ICE cycle and every charge cycle of the battery decreases life expectancies (time wise). SIGNIFICANTLY? Depends on how you, individually define that. If you choose to do it you might want to keep in mind your maintenance schedule. For example, the cycling of the ICE without mileage being accumulated or the effects on the coolant lifespan, again without the corresponding mileage. Ignoring those or miscalculations would almost certainly significantly decrease the lifetime of the vehicle, or at least significantly increase repair costs.

 

The Prius uses very little gas overnight, even in outdoor temperature extremes where the vehicle must run often to maintain 70-72 degrees interior. Less than one gallon for a full overnight. The better check is Distance to Empty. It consistently uses 30 miles worth. If your DTE is over that, you are safe, since that doesn't take into account the 50+ miles the Prius will go when DTE says zero.

 

If your below <=10 F, wouldn't the engine run continuously for heat? I don't think a gallon is going to cut it. OP is in Ontario, Canada.

 

For an idea of fuel consumption when hunkering at cold temperatures in a Gen 3, see here:

on hunkering, Gen 3 style | PriusChat