Menu
AWS Billing and Cost Management
User Guide (Version 2.0)

Reserved Instances

Reserved Instances provide you a significant discount compared to On-Demand Instance pricing. Reserved Instances are not physical instances. They are a billing discount applied to the use of On-Demand Instances in your account. These On-Demand Instances must match certain attributes in order to benefit from the billing discount.

Upfront Fee

The Fee line item is added to your bill when you purchase an All Upfront or Partial Upfront RI. The following screenshot shows how this one-time fee appears in the AWS Cost and Usage report (some columns were omitted for clarity).

Recurring Monthly RI Fee

The RI Fee line item describes the recurring monthly charges that are associated with Partial Upfront and No Upfront RIs. The RI Fee initially is added to your bill on the day of purchase, and on the first day of each billing period thereafter. If you purchase an All Upfront RI, the RI Fee line item is not added to your bill.

The RI Fee is calculated by multiplying your discounted hourly rate and the number of hours in the month. The following screenshot shows how the recurring monthly charges appear in the report.

Note

Recurring monthly charges are recorded differently for RIs that have an Availability Zone (AZ) or region scope. For RIs that have an AZ scope, the corresponding AZ is shown in the reservation/AvailabilityZone column. For RIs that have a region scope, the reservation/AvailabilityZone column is empty. RIs with a region scope have values for the lineitem/NormalizationFactor and reservation/TotalReservedNormalizedUnits columns that show the instance size.

RI Discount Benefits

The Discounted Usage line item describes the instance usage that received a matching RI discount benefit, and is added to your bill when you have usage that matches one of your RIs. AWS calculates RI discount benefits based on matching usage, for example, the use of an instance that matches the instance reservation. If you have matching usage, the cost associated with the usage line item is always zero because the charges associated with RIs are already accounted for in the two other line items (the upfront fee and the recurring monthly charges). The following screenshot shows an example of usage that received an RI discount benefit.

Note

The value for UsageAmount in the Amazon EC2 DiscountedUsage line is the actual number of hours used. The value for NormalizedUsageAmount is the value for UsageAmount multiplied by the value for NormalizationFactor. The value for NormalizationFactor is determined by the instance size. When an RI benefit discount is applied to a matching line item of usage, the ARN value in the reservation/ReservationARN column for the initial upfront fees and recurring monthly charges matches the ARN value in the discounted usage line items.

For more information about mapping instance size to normalization factor, see Modifying the Instance Size of Your Reservations in the Amazon EC2 User Guide for Linux Instances.