It is not shaken by indolent Laziness, thus is it the Power of Energy.
It is the Power of Energy by stiffening & stabilizing other qualities.
It is the Power of Energy by terminating the bad mental defilements.
It is the Power of Energy by purifying penetration to understanding.
It is the Power of Energy by calming, steadying & focusing the mind.
It is the Power of Energy by clearing, cleansing & purifying the mind.
It is the Power of Energy in the sense of arrival at subtle distinction.
It is the Power of Energy in the sense of penetration to even higher.
It is the Power of Energy in the sense of convergence upon actuality.
It is the Power of Energy in the sense of establishing in cessation!
The energetic one has unflagging faith. The faithful one is energetic.
The energetic establishes awareness. The aware one is energetic.
The energetic one concentrates. The concentrated one is energetic.
The energetic one understands. The understanding one is energetic.
This and so is the Power of Energy... Mutually enhancing abilities!

Source: Sariputta - The General of the Dhamma -
The Canonical: Path of Discrimination: Patisambhidamagga. IV + XIX.
http://www.pariyatti.com/book.cgi?prod_id=133494

For a full Study on Energy (Viriya): The root Hero of all Success:
http://What-Buddha-Said.net/drops/III/The_Definition_of_Energy.htm
http://What-Buddha-Said.net/drops/III/The_Arising_of_Energy.htm
http://What-Buddha-Said.net/drops/III/The_Ability_of_Energy.htm
http://What-Buddha-Said.net/drops/III/The_Origin_of_Energy.htm
http://What-Buddha-Said.net/drops/Enthusiastic_is_Energy.htm
http://What-Buddha-Said.net/drops/III/Power_of_Energy.htm
http://What-Buddha-Said.net/drops/III/Ballanced_Energy.htm
http://What-Buddha-Said.net/drops/III/The_Chief_Hero.htm
http://What-Buddha-Said.net/drops/III/Energetic_Effort.htm
http://What-Buddha-Said.net/drops/III/Avoiding_Effort.htm
http://What-Buddha-Said.net/drops/III/Feeding_Energy.htm
http://What-Buddha-Said.net/drops/III/Energy_Viriya.htm
http://What-Buddha-Said.net/drops/III/Dual_Energy.htm