Reserving Amazon EC2 Instances for Long-Term Use
Amazon EC2 now supports an additional pricing option. With Amazon EC2 Reserved Instances, you can make a low one-time payment for each instance to reserve and receive a significant discount on the hourly usage charge for that instance.
Amazon EC2 Reserved Instances are based on instance type and location (region and Availability Zone) for a specified period of time (e.g., 1 year or 3 years).
For information about pricing, refer to the Amazon EC2 Product Page.