Reserved Instances provide you with a significant discount compared to On-Demand instance pricing. In addition, when Reserved Instances are assigned to a specific Availability Zone, they provide a capacity reservation. For more information, see Choosing a Reserved Instance Payment Option.
Reserved Instances are automatically applied to running EC2 instances that match the
Reserved Instance attributes. So, if you purchased two
default tenancy, Linux Reserved Instances for the US East (N. Virginia)
region, up to two
default tenancy, Linux instances
running in the US East (N. Virginia) region can benefit from the Reserved Instance discount.
The same logic applies if you’ve purchased a Reserved Instance for a specific Availability
Zone; however, each Reserved Instance that is specific to an Availability Zone can also
provide a capacity reservation.
When you purchase a Reserved Instance, choose a payment option, term, and an offering class that suits your needs. Generally speaking, you can save more money choosing Reserved Instances with a higher upfront payment. There are three payment options (No Upfront, Partial Upfront, All Upfront) and two term lengths (one-year or three-years). You can find Reserved Instances offered by third-party sellers at shorter term lengths and lower prices as well. The offering class is used to differentiate Convertible Reserved Instances and Standard Reserved Instances. Convertible Reserved Instances can be exchanged during the term for Convertible Reserved Instances with new attributes including instance type. Standard Reserved Instances can be modified during the term, but the instance type is fixed throughout the term.
When you purchase a Reserved Instance, the reservation is automatically applied to running instances that match your specified parameters. Alternatively, you can launch an On-Demand EC2 instance with the same configuration as the reservation, and the billing benefit is applied automatically. No Upfront and Partial Upfront Reserved Instances are billed for usage on an hourly basis, regardless of whether or not they are being used. All Upfront Reserved Instances have no additional hourly charges.
Reserved Instances do not renew automatically; when they expire you can continue using the EC2 instance without interruption, but you will be charged On-Demand rates. New Reserved Instances can have the same parameters as the expired ones, or you can purchase Reserved Instances with different parameters.
You can use Auto Scaling or other AWS services to launch the On-Demand instances that use your Reserved Instance benefits. For information about launching On-Demand instances, see Launch Your Instance. For information about launching instances using Auto Scaling, see the Auto Scaling User Guide.
For product pricing information, see the following pages:
For information about the Reserved Instance pricing tiers, see Understanding Reserved Instance Discount Pricing Tiers.