# Unused EC2 On-Demand Capacity Reservations | Cloud Efficiency Hub Canonical: https://www.pointfive.co/efficiency-hub/inefficiencies/unused-ec2-on-demand-capacity-reservations On-Demand Capacity Reservations (ODCRs) hold EC2 capacity for a specific instance type, platform, tenancy and Availability Zone. By: PointFive Updated: 2026-09-28 [Cloud Efficiency Hub](https://www.pointfive.co/efficiency-hub) The short version On-Demand Capacity Reservations (ODCRs) hold EC2 capacity for a specific instance type, platform, tenancy and Availability Zone. PointFive Research Cloud cost research at PointFive AWS service [AWS EC2](https://www.pointfive.co/efficiency-hub/cloud-services/aws-ec2) Category [Compute](https://www.pointfive.co/efficiency-hub/service-category/compute) Reference CER-0342 Type Idle or Unused Resource ## Explanation Why the waste happens and who it affects. They are billed at the equivalent On-Demand rate for every reserved slot whether or not an instance is running in it. Reservations are often created for a launch, a peak event, a migration or disaster recovery, and then stay in place after the instances that used them are terminated, resized to another type, or moved to another AZ. Because unused capacity appears as an unused reservation line rather than as a running instance, it is easy to overlook in instance-centric reviews. Reservations with targeted matching criteria are especially prone to sitting empty, since only instances that explicitly target them can use them. AWS Health sends underutilization notifications for reservations below 20 percent utilization, but they go to the email address of the account that owns the reservation, so in multi-account organizations they may not reach the team that created it. ## Billing model The pricing dimensions that drive this cost. Unused reservation Each reserved slot without a matching running instance is billed at the On-Demand rate for that instance type and platform Used reservation When a matching instance runs in the reservation, you pay only for the instance and nothing extra for the reservation Billing granularity Per second with a 60-second minimum, from the time the reservation is provisioned until it is canceled or ends Discounts Savings Plans and Regional Reserved Instances can apply to unused reservations, after instance usage is covered; zonal Reserved Instances do not apply Future-dated commitment Future-dated reservations have a commitment duration (minimum 14 days for most types) during which the count cannot drop below the committed number and cancellation may incur a charge ## How to detect 5 checks to find it in your estate. - In CUR 2.0, filter line items where capacity\_reservation\_capacity\_reservation\_status is Unused (line\_item\_usage\_type UnusedBox) and group by reservation to see the cost of idle slots - Monitor the AWS/EC2CapacityReservations CloudWatch metrics AvailableInstanceCount and InstanceUtilization by CapacityReservationId; reservations with persistently high AvailableInstanceCount or low InstanceUtilization are candidates - Create an EventBridge rule for the AWS Health events AWS\_EC2\_ODCR\_UNDERUTILIZATION\_NOTIFICATION (a newly created reservation below 20 percent utilization over 24 hours) and AWS\_EC2\_ODCR\_UNDERUTILIZATION\_NOTIFICATION\_SUMMARY (reservations below 20 percent over 7 days) - List active reservations with describe-capacity-reservations and review those with EndDateType unlimited, no owner tag, or a creation date tied to a past event - For targeted reservations, check whether any launch template or instance still references the reservation or its Capacity Reservation group ## How to fix 6 ways to remove the waste. - Cancel reservations that no longer protect a workload; charges stop when the reservation is canceled, and instances already running in it continue to run as normal On-Demand instances - Reduce the instance count of reservations that are only partly used, keeping only the headroom the workload actually needs - Set an end date and time on reservations created for time-bound events so they expire automatically - If the capacity is still needed but instances are not landing in it, fix the matching: align instance type, platform, tenancy and AZ, switch to open matching, or have launch templates target the reservation or its Capacity Reservation group - For future-dated reservations, check the commitment duration before canceling or reducing, since a cancellation charge may apply during the commitment - Automate cleanup with an EventBridge rule on the underutilization event that notifies owners or triggers a Lambda function to cancel reservations that stay below 20 percent over 7 days ## Documentation Vendor references for pricing and configuration. - [Capacity Reservation pricing and billing docs.aws.amazon.com](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservations-pricing-billing.html) - [Monitor Capacity Reservation underutilization docs.aws.amazon.com](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/cr-eventbridge.html) - [Monitor Capacity Reservations usage with CloudWatch metrics docs.aws.amazon.com](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservation-cw-metrics.html) - [Concepts for Amazon EC2 Capacity Reservations docs.aws.amazon.com](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/cr-concepts.html) - [Amazon EC2 On-Demand Pricing aws.amazon.com](https://aws.amazon.com/ec2/pricing/on-demand/) ## Related inefficiencies [Browse the library](https://www.pointfive.co/efficiency-hub) - AWS EC2 CER-0083 ### [Stale Dedicated Hosts for Stopped EC2 Mac Instances](https://www.pointfive.co/efficiency-hub/inefficiencies/stale-dedicated-hosts-for-stopped-ec2-mac-instances) When an EC2 Mac instance is stopped or terminated, its associated dedicated host remains allocated by default. Because Mac instances run only on Dedicated Hosts (one instance per host) and the host, not the instance, is the unit of... Compute - AWS EC2 CER-0034 ### [Inactive EC2 Instance](https://www.pointfive.co/efficiency-hub/inefficiencies/inactive-ec2-instance) An EC2 instance remains in a running state but is not actively utilized. These instances may be remnants of past projects, forgotten development environments, or temporarily created for testing and never decommissioned. If an instance... Compute - AWS EC2 CER-0343 ### [Underutilized EC2 Dedicated Hosts](https://www.pointfive.co/efficiency-hub/inefficiencies/underutilized-ec2-dedicated-hosts) EC2 Dedicated Hosts are physical servers allocated to a single account, usually to bring existing socket- or core-based licenses (such as Windows Server or SQL Server) or to meet compliance requirements. The host, not the instance, is the... Compute --- Source: the public page above. Product screenshots and illustrative interfaces are examples, not live customer data.