Yes. Capacity Reservation is charged on-demand while provisioning is active.
Billing starts as soon as the Capacity Reservation is provisioned in your account, and it continues while the Capacity Reservation remains provisioned in your account.
Just to clarify (to make sure there are no confusions between Reserved Instances and Reserved Capacity):
- If you talk about On-Demand Capacity Reservation (ODCR) - this is a feature normally used if you run critical workload and need to have the capacity you require when you start/launch your instance. In this case, you pay either for the instance that's running inside that capacity reservation, OR you still pay for the idle capacity reservation while the instance is not running.
- If you mean Reserved Instances - these are mostly used to benefit from the long-term savings for workloads running 24/7 or close to 24/7. You pay for the RI for the full term, regardless if you actually run any matching EC2 instances or not during certain hours of the day.
Depends on the use case. If you are seeking to reserve capacity - ODCR is the right feature. If you are looking for BOTH reserving capacity AND getting billing discount - you can couple ODCR with Savings Plans or Regional Reserved Instances. If you only care about the discount, you should evaluate if your instance will run close to 24/7. Because if not, buying Savings Plan or Reserved Instance may not work for you, as it may end up being more expensive than simply running your instance on-demand for a couple of hours during the day (to make it cheaper, consider Spot pricing; it may be not for all workloads, but if you only run your instance for short periods of time and can handle interuptions - Spot will be the cheapest instance purchasing option).
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