Toyota 2011 Prius Owner's Manual page 201

2-1. Driving procedures
Eco drive mode
Use Eco drive mode to help achieve low fuel consumption during trips
that involve frequent accelerating and braking.
Press the "ECO MODE" switch once more to cancel the Eco drive
mode.
Eco drive mode will not be canceled until the "ECO MODE" switch is
pressed, even if the "POWER" switch is turned to OFF.
2
Press the "PWR MODE" switch to change the driving mode to power
mode.
Power mode
Use when high levels of response and feeling are desirable, such as
when driving in mountainous regions or when overtaking.
Press the "PWR MODE" switch once more to cancel the power mode.
Turning the "POWER" switch to OFF once will cancel power mode.
Press the "ECO MODE" switch to change the driving mode to Eco drive
mode.
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