Missing Reserved PTUs for Steady-State Azure OpenAI Workloads

When usage stabilizes after initial experimentation, continuing to rely on on-demand PTUs results in ongoing unnecessary spend. These workloads are strong candidates for reserved PTUs, which provide identical performance guarantees at a substantially reduced hourly rate. Migrating to reservations requires no architectural changes, because a reservation is a billing discount applied to matching deployments. It must match the deployment type (and, for Data Zone and Regional deployments, the region), does not guarantee capacity, and is not canceled automatically when a deployment is deleted.

PTUs are billed hourly based on the number of PTUs deployed, whether or not the deployment is handling requests. On-demand PTUs use standard hourly rates, whereas reservations apply a discounted effective hourly rate when capacity is committed for one month or one year. The discount varies by deployment type (Global, Data Zone, or Regional), model family, and term, so compare current hourly and reservation prices before committing. Workloads running continuously on on-demand PTUs incur avoidable premium pricing.

• Review PTU deployments supporting production workloads that operate continuously throughout the day
• Assess whether throughput demand remains stable enough to justify reserved capacity
• Identify deployments that have moved beyond experimentation but still use on-demand PTUs
• Evaluate the cost difference between on-demand PTUs and reserved PTUs for these workloads

• Purchase monthly or annual reserved PTUs for workloads with sustained, predictable throughput needs, buying them only after the deployments exist and matching each reservation to the deployment type and region
• Establish governance criteria defining when production PTU deployments should transition to reservations
• Periodically reassess workload stability to ensure PTU reservation commitments remain aligned with demand
• Use cost modeling to evaluate reservation options as part of production readiness reviews

• Save costs with Microsoft Foundry Provisioned Throughput Reservationslearn.microsoft.com
• Provisioned throughput billing and cost managementlearn.microsoft.com