It takes a lot of energy to bring about the tides. What is that energy tapped from? The impetus of the moon?

Answer 1

The gravity of the moon. Gravity pulls on everything. The moon's gravity pulls on everything on the earth, but only the oceans show the pull in a way we can measure.

Answer 2

First of all, Jay Ingram's Book of Everyday Science (I recommend you read it) says that there is no such thing as impetus. Second, it's gravity that pulls on the tide. If gravity is strong enough to bring down buildings, it's strong enough to pull the tide.