The French Orthodox theologian Olivier Clement (1921-2009) in his The Roots of Christian Mysticism (New City Press 1993) succinctly ties together the Eastern Christian concepts of  divine essence, divine energies, and the process of theosis or divinization.  The quote is found on pp 237-238.

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The Fathers distinguish here, without in any way separating them, the inaccessible essence of God and the energy (or energies) by means of which his essence is made inexhaustibly capable of being shared in.  It is a distinction that is inherent in the reality of the divine Persons and it points, on the one hand, to their secret nature and, on the other hand, to the communication of their love and their life.  The essence does not imply a depth greater than the Trinity; it means the depth in the Trinity, the depth that cannot be objectivized, of personal existence in communion.  The inaccessibility of the essence means that God reveals himself of his own free will by grace, by a "folly of love" (St Maximus's expression).  God in his nearness remains transcendent.  He is hidden, not as if in forbidden darkness, but by the very intensity of his light.  It is only God's inaccessibility that allows the positive space for the development of love through which communion is renewed.  God overcomes otherness in himself without dissolving it and that is the mystery of the Trinity in Unity.  He overcomes it in his relations with us, again without dissolving it, and that is the distinction-identity of the reality and the energies.  "God is altogether shared and altogether unshareable", as Dionysius the Aeropagite and Maximus the Confessor say.  The energy is the expansion of the Trinitarian love.  It associates us with the perichoresis of the divine Persons.

God as inaccessible essence--transcendent, always beyond our reach. 

God as energy capable of being shared in--God incarnate, crucified, descended  into hell, risen from the dead and raising us up, that is, enabling us to share in his life, even from the starting point of our own enclosed hell--God always within our reach.

The energy--or energies--can therefore be considered from two complementary standpoints.  On the one hand is life, glory, the numberless divine Names that radiate eternally from the essence.  From all eternity God lives and reigns in glory.  And the waves of his power permeate the universe from the moment of its creation, bestowing on it its translucent beauty, masked partially by the fall.  At the same time, however, the energy or energies that create and maintain the universe, and then enable it to enter potentially into the realm of the Spirit, and to be offered the risen life.  All these operations therefore are summed up in Jesus, the name that means "God saves", "God frees", "God sets at liberty".  In his person humanity and all creation are "authenticated", "spiritulalized", "vivified", since, as St Paul saves, "in him [Christ] the whole fullness of deity dwells  bodily" (Col 2: 9).  The energy as divine activity ensures our share in the energy as divine life, since what God gives us is himself.  The energy is not an impersonal emanation nor is it a part of God.  It is that life that comes from the Father through the Son in the Holy Spirit.  It is that life that flows from the whole being of Jesus, from his pierced side, from his empty tomb.  It is that power that is God giving himself entirely while remaining entirely above and beyond creatures.