Explanation
Why the waste happens and who it affects.
When this happens, the committed usage goes unused, while new workloads run on non-covered SKUs, resulting in both underutilized reservations and full-price on-demand charges elsewhere.
The root inefficiency is architectural or operational drift away from what was originally committed - often due to team autonomy, poor RI governance, or legacy commitments. This leads to silent waste unless workloads are re-aligned to match existing reservations.
Billing model
The pricing dimensions that drive this cost.
- Azure Reservations are prepaid or monthly-commit financial instruments
- The discount applies only to matching resources in the reserved region; for VM reservations optimized for instance size flexibility, it also covers other sizes in the same instance size flexibility group
- Underutilized reservations result in sunk cost with no usage offset
- Azure offers limited flexibility via instance size flexibility, re-scoping, exchange options (restricted for many services from February 1, 2027), or trade-in to a savings plan
How to detect
4 checks to find it in your estate.
- Identify Azure Reservations with consistently low utilization rates
- Determine which SKUs, regions, or resource types are covered but underused
- Compare current usage patterns to reservation scope (e.g., VM series, region, size)
- Assess whether workloads moved off the committed types due to organic evolution, performance needs, or misaligned provisioning
How to fix
5 ways to remove the waste.
- Evaluate whether any existing workloads could be migrated to match the reservation scope
- For new workloads, consider provisioning on RI-covered instance types when technically viable
- Where appropriate, exchange the reservation for a more relevant SKU, or trade it in for an Azure savings plan; from February 1, 2027, reservations for savings-plan-eligible services (such as VMs, App Service, and SQL Database) bought after that date can't be exchanged, and those bought earlier keep one final exchange
- Re-scope the reservation (shared, management group, subscription, or resource group) if cross-team usage can improve coverage; changing the region requires an exchange
- Use RI utilization data to inform future purchasing decisions and reduce overcommit risk
Documentation
Vendor references for pricing and configuration.