When we pray with power, God responds to our petitions by releasing His supernatural might toward the object or the areas we are concerned about. There is a difference in saying prayers and genuinely praying with power. Prayer that releases God's supernatural power has a strong desire. It is engaging, fervent, and persistent. It must come from a thirsting, tenacious heart that boldly seeks God and His kingdom.
People often say there is power in prayer.
There is no power in the prayer itself. The power is in God, and is released from Him. Omnipotent God executes change as a result of our praying. So, when He says the effective prayer of a righteous man avails much, He simply means that in response to the prayer of righteous men and women, the supernatural power of God is released and directed toward the object of their concern or petition. When you and I begin to pray for someone else, that person becomes the target of God's power.