Use your Reserved Instances

Reserved Instances are automatically applied to running On-Demand Instances provided that the specifications match. If you have no running On-Demand Instances that match the specifications of your Reserved Instance, the Reserved Instance is unused until you launch an instance with the required specifications.

If you're launching an On-Demand Instance to take advantage of the billing benefit of a Reserved Instance, ensure that you specify the following information when you configure your On-Demand Instance:

Platform

You must specify an Amazon Machine Image (AMI) that matches the platform (product description) of your Reserved Instance. For example, if you specified Linux/UNIX for your Reserved Instance, you can launch an instance from an Amazon Linux AMI or an Ubuntu AMI.

Instance type

If you purchased a zonal Reserved Instance, you must specify the same instance type as your Reserved Instance; for example, t3.large. For more information, see How zonal Reserved Instances are applied.

If you purchased a regional Reserved Instance, you must specify an instance type from the same instance family as the instance type of your Reserved Instance. For example, if you specified t3.xlarge for your Reserved Instance, you must launch your instance from the T3 family, but you can specify any size, for example, t3.medium. For more information, see How regional Reserved Instances are applied.

Availability Zone

If you purchased a zonal Reserved Instance for a specific Availability Zone, you must launch the instance into the same Availability Zone.

If you purchased a regional Reserved Instance, you can launch the instance into any Availability Zone in the Region that you specified for the Reserved Instance.

Tenancy

The tenancy (dedicated or shared) of the instance must match the tenancy of your Reserved Instance. For more information, see Amazon EC2 Dedicated Instances.

For examples of how Reserved Instances are applied to your running On-Demand Instances, see How Reserved Instance discounts are applied. For more information, see Why aren't my Amazon EC2 Reserved Instances applying to my AWS billing in the way that I expected?

You can use various methods to launch the On-Demand Instances that use your Reserved Instance discount. For information about the different launch methods, see Launch an Amazon EC2 instance. You can also use Amazon EC2 Auto Scaling to launch an instance. For more information, see the Amazon EC2 Auto Scaling User Guide.