1# Capacity Reservation Overview
2 
3Reference material for Azure Capacity Reservation Groups and Capacity Reservations.
4 
5## What Is a Capacity Reservation Group?
6 
7A Capacity Reservation Group (CRG) is a logical container for one or more capacity reservations. It acts as the association point for VMs and VMSS — you associate a VM or scale set with the **group**, and Azure matches the VM to a suitable reservation within that group.
8 
9## Constraints
10 
11| Constraint                     | Detail                                                                                                     |
12|--------------------------------|------------------------------------------------------------------------------------------------------------|
13| **Region-scoped**              | A CRG and all its reservations must be in the same Azure region                                            |
14| **Zone-specific**              | Each reservation targets a specific Availability Zone (or is non-zonal)                                    |
15| **Subscription-scoped**        | A CRG lives in a single subscription but can be shared with other subscriptions via the `sharing` property |
16| **VM size per reservation**    | Each capacity reservation covers exactly one VM size                                                       |
17| **Billing starts immediately** | You are charged for reserved capacity whether or not VMs are running against it                            |
18 
19## Association and Disassociation
20 
21See [association-disassociation.md](association-disassociation.md) for how to associate and disassociate VMs/VMSS with a CRG.
22 
23## Common CLI Commands
24 
25| Action                      | Command                                                                                                     |
26|-----------------------------|-------------------------------------------------------------------------------------------------------------|
27| List CRGs                   | `az capacity reservation group list`                                                                        |
28| Show CRG                    | `az capacity reservation group show -g <rg> -n <crg> --instance-view`                                       |
29| Delete CRG                  | `az capacity reservation group delete -g <rg> -n <crg>`                                                     |
30| List reservations           | `az capacity reservation list -g <rg> --capacity-reservation-group <crg>`                                   |
31| Update reservation quantity | `az capacity reservation update -g <rg> --capacity-reservation-group <crg> -n <res> --capacity <new-count>` |
32| Delete reservation          | `az capacity reservation delete -g <rg> --capacity-reservation-group <crg> -n <res>`                        |
33 
34## Finding Valid CRGs for a VM
35 
36To associate a VM with a CRG, the CRG must contain a capacity reservation that matches the VM's **size**, **region**, and **zone** (if zonal). While `az capacity reservation group list` can enumerate CRGs at the subscription level, filtering down to matching reservations across many groups is inefficient. Azure Resource Graph is recommended for cross-resource-group discovery.
37 
38### Option 1: Azure Resource Graph (recommended)
39 
40ARG can query all capacity reservations across resource groups in a single call, filtering by location, VM size, and zone. This is the most efficient approach.
41 
42> ⚠️ **Prerequisite:** `az extension add --name resource-graph`
43 
44You must collapse this query to a **single line** before running it:
45 
46```bash
47az graph query -q "
48  Resources
49  | where type =~ 'Microsoft.Compute/capacityReservationGroups/capacityReservations'
50  | where location =~ '<region>'
51  | where properties.provisioningState =~ 'Succeeded'
52  | where sku.name =~ '<vm-size>'
53  | project id,
54            crgId = extract('(.*)/capacityReservations', 1, id),
55            resourceGroup,
56            zones,
57            size = sku.name,
58            capacity = coalesce(sku.capacity, 0),
59            associationCount = coalesce(array_length(properties.virtualMachinesAssociated), 0),
60            location
61" --query "data[]" -o table
62```
63 
64The `crgId` in the output is the parent Capacity Reservation Group resource ID — this is the value to use when associating a VM or VMSS.
65 
66To further narrow results for zonal VMs, add a zone filter:
67 
68```kql
69| where zones has '<zone>'
70```
71 
72### Option 2: CLI enumeration
73 
74If ARG is unavailable, list CRGs per resource group and inspect their reservations:
75 
76```bash
77# List all CRGs
78az capacity reservation group list -o table
79 
80# List reservations within a CRG and check for matching size/capacity
81az capacity reservation list \
82  -g <rg> \
83  --capacity-reservation-group <crg-name> \
84  --query "[?sku.name=='<vm-size>'].{name:name, size:sku.name, capacity:sku.capacity, zones:zones}" \
85  -o table
86```
87 
88## Estimating Reservation Cost
89 
90Capacity reservations are billed at the same pay-as-you-go rate as the underlying VM size, whether or not VMs are running against them. Use the [Retail Prices API guide](../../../references/retail-prices-api.md) (unauthenticated) to look up hourly rates.
91 
92**Estimated monthly cost:** `quantity × hourly rate × 730`
93 
94> ⚠️ Prices returned are **estimates based on current retail pay-as-you-go rates**, not a final cost or contractual commitment. Actual charges may vary due to taxes, discounts (Reserved Instances, Savings Plans), or price changes.
95 
96## Important Notes
97 
98- **Deletion is blocked until prerequisites are met:** Azure rejects a CRG delete unless all VMs/VMSS are disassociated and all capacity reservations are deleted. Order: disassociate VMs/VMSS → delete reservations → delete group.
99- **Quota required:** Capacity reservations consume vCPU quota just like running VMs.
100 
101## Learn More
102 
103- [Azure Capacity Reservations documentation](https://learn.microsoft.com/en-us/azure/virtual-machines/capacity-reservation-overview)
104- [Create a Capacity Reservation](https://learn.microsoft.com/en-us/azure/virtual-machines/capacity-reservation-create)
105- [Association and disassociation](association-disassociation.md)
106