GCP Committed Use Discounts vs Sustained Use Discounts: The Complete Guide

GCP's Unique Discount Approach

Google Cloud uses a distinctive discount model that differs significantly from AWS and Azure. Understanding both discount types is key to minimising GCP costs.

Sustained Use Discounts (SUDs) — Automatic

GCP automatically applies SUDs when you run an instance for more than 25% of the month — no action required. The discount increases the longer the instance runs:

For instances running 24/7, SUDs automatically apply a 20-30% discount. This is why GCP often appears cheaper than AWS at first glance — the base price includes potential SUD.

Committed Use Discounts (CUDs) — Manual Commitment

For deeper discounts, commit to consistent resource usage for 1 or 3 years:

CUDs vs AWS/Azure Reservations

Key advantage of GCP CUDs: you commit to a resource amount (vCPUs and RAM), not a specific instance type. Your CUD applies to any VM that fits within your committed resource pool — giving more flexibility than AWS Standard RIs.

Combining CUDs and SUDs

You can stack CUDs on top of SUDs — commit to 50% of your baseline workload with CUDs, and any additional usage gets SUDs automatically applied. This hybrid approach is optimal for workloads with variable peaks.

Spot/Preemptible Instances

For interruptible workloads: GCP Spot VMs offer up to 91% discount. GKE Autopilot supports Spot pods for even deeper savings on containerised workloads.

For stable 24/7 workloads, CUDs are always better than relying on SUDs alone. Calculate your baseline and commit to it — your remaining dynamic workload gets SUDs automatically.