# How to Fix InsufficientInstanceCapacity Error in AWS EC2

Suppose AWS doesn't currently have enough available On-Demand capacity to complete your request. In that case, you may encounter the **InsufficientInstanceCapacity** error when you try to launch a new instance or restart a stopped instance.

## Resolution Steps

### 1\. Wait and Retry

AWS capacity can shift frequently. If you encounter this error, wait and then submit your request again.

### 2\. Change the Instance Type

If waiting does not resolve the issue, try changing the instance type:

* Navigate to **Actions > Instance Settings > Change Instance Type**.
    
* Select the desired instance type.
    

**Note:** Ensure you take a backup of the instance before making changes.

### 3\. Move the Instance

If changing the instance type does not work, move the instance to another **VPC**, **subnet**, or **Availability Zone**.

[move-ec2-instance](https://repost.aws/knowledge-center/move-ec2-instance)

## Avoiding Insufficient Capacity Errors on Critical Machines

To ensure that critical machines are not affected by capacity issues, consider creating **On-Demand Capacity Reservations** in advance.

### Steps to Use On-Demand Capacity Reservations:

1. **Create the Capacity Reservation** in a specific Availability Zone. Follow the official AWS guide [here](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservations-create.html#capacity-reservations-create).
    
2. **Launch critical instances** into the Capacity Reservation. Refer to the AWS guide on [launching instances into Capacity Reservations](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservations-create.html#capacity-reservations-launch).
    
3. **Monitor usage** in real-time and launch instances into it as needed.
    

For a comprehensive understanding of Capacity Reservations, visit the [AWS EC2 Capacity Reservations documentation](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-capacity-reservations.html).

**Note:** Be aware that charges are associated with Capacity Reservations. They are billed at the equivalent On-Demand rate, whether the reserved capacity is utilized or not. If the reservation remains unused, it will appear as an **unused reservation** on your Amazon EC2 bill.

For more details, refer to the official AWS documentation on [**Capacity Reservations Pricing**](https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/capacity-reservations-pricing-billing.html).