The importance of energy in a dance is very plain to see. Because I play lacrosse this is easiest for me to describe in terms of a sporting event. While energy is intangible and more of a concept than an actual entity the importance of it is no less. When watching a lacrosse game it is as plain as night and day whether an athlete has energy. Their movements are done quickly and purposefully. An athlete with little or no energy moves lethargically they are no fun to watch and are not effective on the field. This is also true of dancing and the way a dancer performs.
The energy creates the feeling of a dance. Dances preformed with a great deal of energy will usual appear up beat and fast. Also when a dance is done with a lot of energy it is usual more captivating and interesting. This is probably because the amount of energy one puts into an action is usually equivalent to the amount of effort as well. Therefore a performance done with a lot of energy will be perceived as better one.
Another aspect of energy that is important to dance is the ability of the dancer to visualize what is occurring in their body while dancing. The exercises in our book tell us to imagine the energy flowing from different areas in channels to our body or from one part of our body to another. This gives me glimpse into the inner workings of my body while I am dancing and also translates to me performing moves in a different way. For example viewing the energy in your body moving like a faucet at first starting as just a trickle and then becoming a rushing torrent makes you move in a very different and more specific way. This visualization of the flow of energy helps me to create different looking movements then I would normally do. As the text says, "energy can be seen clearly" and since other people view dance it is important to have a lot of it and use it creatively.