Reference

Ephesians 1:15-23
The Ascension of Christ - Part 2

God's great power, the very power which raised Jesus from the dead and empowered His ascension back to glory to take His seat at God's right hand, is given to every believer at the time of salvation and is always available.  Consequently, Paul didn't pray that God's power be given to believers but rather that they be aware of the power they already possessed in Christ and utilize it.