Explanation
Why the waste happens and who it affects.
When EC2 workloads shift across instance families or OS types, the original RI may no longer apply to active usage. If the RI is not converted, the customer continues paying for unused commitment despite having the ability to adapt it.
Because conversion is a manual process and requires matching or exceeding the original RI's value, many organizations fail to optimize their coverage. Over time, this leads to growing pools of ineffective RIs that could have been aligned to real workloads.
Billing model
The pricing dimensions that drive this cost.
- Convertible RIs are billed hourly based on the original reservation terms
- Charges continue regardless of actual instance usage
- RIs must be actively converted to align with changing usage - past underutilization is not refunded
How to detect
4 checks to find it in your estate.
- Identify Convertible RIs with low utilization over a trailing period
- Compare current EC2 usage to the instance types, families, and configurations reserved under each RI
- Highlight RIs that are eligible for conversion but remain mismatched to actual compute patterns
- Evaluate how much unused commitment could be recovered through a conversion
How to fix
4 ways to remove the waste.
- Use the AWS Management Console or CLI to convert unused Convertible RIs to match current EC2 instance usage
- Ensure the new reservation configuration has equal or greater value, as required by AWS
- Monitor usage regularly to identify when new conversions may be needed
- Build RI optimization reviews into quarterly infrastructure hygiene practices to prevent recurring waste
Documentation
Vendor references for pricing and configuration.