Schau mal hier http://avrhelp.mcselec.com/ bei POWER mode

The mode depends on the micro processor.
Some valid options are :
- IDLE
- POWERDOWN
- STANDBY
- ADCNOISE
- POWERSAVE

So for standby you would use : POWER STANDBY
It is also possible to use POWERDOWN, IDLE or POWERSAVE. These modes were/are supported by most processors. It is recommended to use the new POWER command because it allows to use more modes.

POWER has nothing to do with the POWER() function.