Toyota Prius Owner's Manual page 361

CAUTION

When the outside rear view mirror defoggers are on
Do not touch the outside surface of the rear view mirrors, as they can
become very hot and burn you.
NOTICE

To prevent 12-volt battery discharge
Do not leave the rear window defogger on longer than necessary when the
hybrid system is off.
PRIUS_OM_OM47A19E_(EE)
3-1. Using the air conditioning system and defogger
3
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