Reserved Instances are a billing discount and capacity reservation that is applied to instances to lower hourly running costs. A Reserved Instance is not a physical instance. The discounted usage price is fixed for as long as you own the Reserved Instance, allowing you to predict compute costs over the term of the reservation. If you are expecting consistent, heavy, use, Reserved Instances can provide substantial savings over owning your own hardware or running only On-Demand instances. For more information, see Choosing a Reserved Instance Payment Option.
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 purchased reserved capacity. 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; 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 Developer Guide.
For product pricing information, see the following pages:
For information about the Reserved Instances pricing tiers, see Understanding Reserved Instance Discount Pricing Tiers.
Light, Medium, and Heavy Utilization Reserved Instances are no longer available for purchase. For more information about how these instances are affected by changes to the Reserved Instances pricing model, see Reserved Instance FAQ.