In chapter 13 of his book, Why There Is No God, author Armin Navabi takes on the claim that, "God is love; God is energy." Much of this chapter is focused on the meaning of words and rebutting the argument that "God is energy." To be honest, in my 32 years of walking as a Christian, I've never heard the argument that, "God is energy," used as a proof for God's existence. It seems rather silly to me and I don't really understand why Navabi pays so much attention to it, except perhaps to make certain people look silly for positing such a silly argument. However, it's a bit different when we say, as the Bible does, that, "God is love."
In the beginning of the chapter, Navabi notes, "If you claim that God exists but cannot say exactly what God is, your claim is ultimately meaningless." I agree with him on this point, as I argued in my response to his chapter that God cannot be comprehended. God can be understood and there are many ways that we can explain and explore his character since he has given us many of his same character traits so that we can have a basis for interacting with him.
The notion that God is love comes from I John 4:15-16, "Whoever confesses that Jesus is the Son of God, God abides in him, and he in God. So we have come to know and to believe the love that God has for us. God is love, and whoever abides in love abides in God, and God abides in him."
This reference serves as a description to help us understand the primary character trait that moves God to do what he does. His acts of creation and relation are born out of his love for doing good and enjoying his people.
Now, Navabi has a point. Saying that God is love isn't really proving to the atheist that God exists. Such a statement is a statement about God's character. So also would be a statement like, "God is good," or "God is merciful." These statements don't do anything to prove to the atheist that God exists. But they do make the case that the God of the Bible is worth believing in since his character is motivated by his love for us and his actions for his people are actions of love. This is unique in the world of religions. The Allah of Islam is not motivated by love, but by will. Even according to Islamic theology no one can personally experience Allah's love. Eastern religions know nothing of this either.
This is a comforting thing. God's love has motivated many people to come to faith in him. As the Four Spiritual Laws states, "God loves you and has a wonderful plan for your life." When someone experiences God's love, then in that moment a person has an experience where he understands that God is actually real and cares about him or her. Navabi might argue that such an experience is subjective (implying that it is unreal), but it doesn't invalidate the experience.
God is love. Saying so may not prove that he exists, but it does reveal the ultimate meaning behind all that God does in relationship with him. I don't know about you, but that energizes me.