Is love an act of the will, or an emotion?
We believe that love is indeed an act of the will. But we need to go one step further and affirm that love is also an emotion. Affections are part of the essence of love. These emotions might not always be intense, but they are always there to some extent.
One piece of evidence for this is found in 1 Corinthians 13:1-3, where Paul says that you can give away all your possessions to the poor and still not have love. Evidently, then, love is more than an act of the will, because you can have a sacrificial act of the will without having love. Also note that in 1 Corinthians 13:4-7, love is said to involve various affections: "Love is patient and kind; love does not envy or boast; it is not arrogant or rude. It does not insist on its own way; it is not irritable or resentful; it does not rejoice at wrongdoing, but rejoices with the truth. Love bears all things, believes all things, hopes all things, endures all things."
That love involves not only the will, but also the affections, is born out in everyday experience. Imagine a husband who seeks the welfare of his wife, but doesn't enjoy doing it. Would his wife feel loved? We doubt it. Even if the husband did not dislike serving his wife, but simply was indifferent in doing it, she still would not feel loved. This is because we intuitively recognize that emotions are an essential part of love. Love includes not just willing, but also preferring and wanting and delighting.
John Piper, Desiring God, chapter 4, "Love: The Labor of Christian Hedonism"