Mountain Lion: About Power Nap
Macs that use Power Nap
The MacBook Air (Late 2010, Mid 2011, Mid 2012) and MacBook Pro (Retina, Mid 2012) running Mountain Lion can use Power Nap.
An SMC update is required to gain all the functionality of Power Nap. Here is a list of the supported Macs and the SMC update that is required to support Power Nap: