This packages was mainly intended for laptops. However more and more features (proper suspend/standby, configure ACPI Buttons, processor frequency scaling (also supported on multi processor machines), spinning down the hard disk, thermal management, ...) became available for workstations and even on servers.
This package unifies the control of power managing facilities on your PC. It supports hardware based on ACPI, APM, IDE-disks and CPU frequency scaling techniques. It takes over functionalities of the APMD, ACPID, OSPMD and CPUFREQD (now called CPUSPEED) packages. Therefore you should not install at least you must not run daemons from these packages when you run the powersave daemon!
If your PC does not contain all of the described hardware above (APM and ACPI are mutal exclusive) you should still run this daemon to manage power saving related tasks. The overhead is small and you will be provided with a unique interface and configuration environment. And you can still use this tool if some hardware should change (e.g. booting ACPI instead of APM when kernel provides better ACPI support). The daemon will automatically detect your hardware and support available features.