The term, eternal, with respect to Deity does not mean that God exists in infinite time. If God were to exist in time, He would be measured by time. Eternal means to be not temporal or to not exist in time. God created time. By contrast, temporal means to exist in time.
Humans are temporal beings whose existence can be measure by time.
Absolute infinite power was displayed during the event of the creation of the universe. In other words, there was not an infinite storehouse of power or energy that God took and used to create the universe. Before creation, there was only Deity. Power, energy, and mass are all creatures. Thus, it is obvious that God did not use energy to create the material universe, since matter and energy are equivalent terms.