Billing Charges Related to AWS Compute Optimizer.

We currently have an EC2 instance with an EBS attached. We plan to opt in for Compute optimizer Service to find the most suitable type of EC2 instance for our workload. Right now we do not pay any charges for Cloud watch though we see some metric displayed in the cloud watch/EC2 dashboard. We would like to know if there would be any additional charges for Cloud Watch if we Opt-in for the Compute-Optimizer.