Toyota 2015 Prius Owner's Manual page 363

3-1. Using the air conditioning system and defogger
CAUTION
To prevent the windshield from fogging up
■
Do not use
The difference between the temperature of the outside air and that of the
windshield can cause the outer surface of the windshield to fog up, blocking
your vision.
NOTICE
To prevent 12-volt battery discharge
■
Do not leave the air conditioning system on longer than necessary when the
hybrid system is not operating.
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during cool air operation in extremely humid weather.